--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2356,25 +2356,29 @@ dependencies = [
  "time 0.1.38 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "webrender_bindings"
 version = "0.1.0"
 dependencies = [
  "app_units 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "bincode 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "core-foundation 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "core-graphics 0.13.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "dwrote 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "euclid 0.17.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "foreign-types 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "fxhash 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "gleam 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "nsstring 0.1.0",
  "rayon 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "thread_profiler 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "uuid 0.1.18 (registry+https://github.com/rust-lang/crates.io-index)",
  "webrender 0.57.2",
 ]
 
 [[package]]
 name = "which"
 version = "1.0.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [

--- a/caps/nsScriptSecurityManager.cpp
+++ b/caps/nsScriptSecurityManager.cpp
@@ -1248,25 +1248,16 @@ nsScriptSecurityManager::GetDocShellCode
                                                       nsIPrincipal** aPrincipal)
 {
   nsCOMPtr<nsIPrincipal> prin =
     BasePrincipal::CreateCodebasePrincipal(aURI, nsDocShell::Cast(aDocShell)->GetOriginAttributes());
   prin.forget(aPrincipal);
   return *aPrincipal ? NS_OK : NS_ERROR_FAILURE;
 }
 
-// static
-nsIPrincipal*
-nsScriptSecurityManager::doGetObjectPrincipal(JSObject *aObj)
-{
-    JSCompartment *compartment = js::GetObjectCompartment(aObj);
-    JSPrincipals *principals = JS_GetCompartmentPrincipals(compartment);
-    return nsJSPrincipals::get(principals);
-}
-
 NS_IMETHODIMP
 nsScriptSecurityManager::CanCreateWrapper(JSContext *cx,
                                           const nsIID &aIID,
                                           nsISupports *aObj,
                                           nsIClassInfo *aClassInfo)
 {
 // XXX Special case for Exception ?
 

--- a/caps/nsScriptSecurityManager.h
+++ b/caps/nsScriptSecurityManager.h
@@ -88,20 +88,16 @@ private:
 
     // Decides, based on CSP, whether or not eval() and stuff can be executed.
     static bool
     ContentSecurityPolicyPermitsJSAction(JSContext *cx);
 
     static bool
     JSPrincipalsSubsume(JSPrincipals *first, JSPrincipals *second);
 
-    // Returns null if a principal cannot be found; generally callers
-    // should error out at that point.
-    static nsIPrincipal* doGetObjectPrincipal(JSObject* obj);
-
     nsresult
     Init();
 
     nsresult
     InitPrefs();
 
     inline void
     ScriptSecurityPrefChanged();

--- a/devtools/client/debugger/new/README.mozilla
+++ b/devtools/client/debugger/new/README.mozilla
@@ -1,13 +1,13 @@
 This is the debugger.html project output.
 See https://github.com/devtools-html/debugger.html
 
-Version 60
+Version 61
 
-Comparison: https://github.com/devtools-html/debugger.html/compare/release-59...release-60
+Comparison: https://github.com/devtools-html/debugger.html/compare/release-60...release-61
 
 Packages:
 - babel-plugin-transform-es2015-modules-commonjs @6.26.2
 - babel-preset-react @6.24.1
 - react @16.2.0
 - react-dom @16.2.0
 - webpack @3.11.0

--- a/devtools/client/debugger/new/dist/debugger.css
+++ b/devtools/client/debugger/new/dist/debugger.css
@@ -2112,16 +2112,20 @@ menuseparator {
   color: var(--string-color);
   border-width: 1px;
   border-style: solid;
   border-radius: 2px;
   font-size: 0.8em;
   padding: 0 2px;
 }
 
+.objectBox-node.clickable {
+  cursor: pointer;
+}
+
 /******************************************************************************/
 
 .objectBox-event,
 .objectBox-eventLog,
 .objectBox-regexp,
 .objectBox-object {
   color: var(--object-color);
   white-space: pre-wrap;
@@ -2218,16 +2222,17 @@ menuseparator {
 
 button.open-inspector {
   mask: url("chrome://devtools/skin/images/devtools-reps/open-inspector.svg") no-repeat;
   display: inline-block;
   background-color: var(--comment-node-color);
   height: 16px;
   margin-left: 0.25em;
   vertical-align: middle;
+  cursor: pointer;
 }
 
 .objectBox-node:hover .open-inspector,
 .objectBox-textNode:hover .open-inspector,
 .open-inspector:hover {
   background-color: var(--theme-highlight-blue);
 }
 

--- a/devtools/client/debugger/new/dist/parser-worker.js
+++ b/devtools/client/debugger/new/dist/parser-worker.js
@@ -1217,17 +1217,17 @@ function isAwaitExpression(path) {
 }
 
 function isYieldExpression(path) {
   const { node, parent } = path;
   return t.isYieldExpression(node) || t.isYieldExpression(parent.init) || t.isYieldExpression(parent);
 }
 
 function isObjectShorthand(parent) {
-  return t.isObjectProperty(parent) && parent.key.start == parent.value.start && parent.key.loc.identifierName === parent.value.loc.identifierName;
+  return t.isObjectProperty(parent) && parent.value && parent.key.start == parent.value.start && parent.key.loc.identifierName === parent.value.loc.identifierName;
 }
 
 function getObjectExpressionValue(node) {
   const { value } = node;
 
   if (t.isIdentifier(value)) {
     return value.name;
   }

--- a/devtools/client/debugger/new/dist/vendors.js
+++ b/devtools/client/debugger/new/dist/vendors.js
@@ -8169,17 +8169,17 @@ var _Svg2 = _interopRequireDefault(_Svg)
 function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
 
 function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key]; } } newObj.default = obj; return newObj; } }
 
 // We cannot directly export literals containing special characters
 // (eg. "my-module/Test") which is why they are nested in "vendored".
 // The keys of the vendored object should match the module names
 // !!! Should remain synchronized with .babel/transform-mc.js !!!
-const vendored = {
+const vendored = exports.vendored = {
   classnames: _classnames2.default,
   "devtools-components": devtoolsComponents,
   "devtools-config": devtoolsConfig,
   "devtools-contextmenu": devtoolsContextmenu,
   "devtools-environment": devtoolsEnvironment,
   "devtools-modules": devtoolsModules,
   "devtools-splitter": _devtoolsSplitter2.default,
   "devtools-utils": devtoolsUtils,
@@ -8205,17 +8205,16 @@ const vendored = {
  * same way:
  * - always with destructuring (import { a } from "modA";)
  * - always without destructuring (import modB from "modB")
  *
  * Both are fine, but cannot be mixed for the same module.
  */
 
 // Modules imported with destructuring
-exports.vendored = vendored;
 
 /***/ }),
 
 /***/ 4:
 /***/ (function(module, exports) {
 
 module.exports = __WEBPACK_EXTERNAL_MODULE_4__;
 

--- a/devtools/client/debugger/new/src/actions/pause/extra.js
+++ b/devtools/client/debugger/new/src/actions/pause/extra.js
@@ -86,15 +86,15 @@ function getExtra(expression, result) {
     dispatch,
     getState,
     client,
     sourceMaps
   }) => {
     const selectedFrame = (0, _selectors.getSelectedFrame)(getState());
 
     if (!selectedFrame) {
-      return;
+      return {};
     }
 
     const extra = await getExtraProps(getState, expression, result, expr => client.evaluateInFrame(expr, selectedFrame.id));
     return extra;
   };
 }
\ No newline at end of file

--- a/devtools/client/debugger/new/src/client/index.js
+++ b/devtools/client/debugger/new/src/client/index.js
@@ -1,14 +1,14 @@
 "use strict";
 
 Object.defineProperty(exports, "__esModule", {
   value: true
 });
-exports.onConnect = undefined;
+exports.onConnect = onConnect;
 
 var _firefox = require("./firefox");
 
 var firefox = _interopRequireWildcard(_firefox);
 
 var _prefs = require("../utils/prefs");
 
 var _dbg = require("../utils/dbg");
@@ -63,11 +63,9 @@ async function onConnect(connection, {
   });
   (0, _bootstrap.bootstrapApp)(store);
   return {
     store,
     actions,
     selectors,
     client: commands
   };
-}
-
-exports.onConnect = onConnect;
\ No newline at end of file
+}
\ No newline at end of file

--- a/devtools/client/debugger/new/src/components/Editor/Preview/Popup.js
+++ b/devtools/client/debugger/new/src/components/Editor/Preview/Popup.js
@@ -232,17 +232,17 @@ class Popup extends _react.Component {
 
     let header = null;
 
     if ((0, _preview.isImmutable)(this.getObjectProperties())) {
       header = this.renderImmutable(extra.immutable);
       roots = roots.filter(r => r.type != NODE_TYPES.PROTOTYPE);
     }
 
-    if ((0, _preview.isReactComponent)(this.getObjectProperties())) {
+    if (extra.react && (0, _preview.isReactComponent)(this.getObjectProperties())) {
       header = this.renderReact(extra.react);
       roots = roots.filter(r => ["state", "props"].includes(r.name));
     }
 
     return _react2.default.createElement("div", {
       className: "preview-popup"
     }, header, this.renderObjectInspector(roots));
   }

--- a/devtools/client/debugger/new/src/components/PrimaryPanes/SourcesTree.js
+++ b/devtools/client/debugger/new/src/components/PrimaryPanes/SourcesTree.js
@@ -119,157 +119,166 @@ class SourcesTree extends _react.Compone
         debuggeeUrl,
         projectRoot,
         uncollapsedTree,
         sourceTree
       }));
     }
   }
 
+  // NOTE: we get the source from sources because item.contents is cached
+  getSource(item) {
+    return this.props.sources.get(item.contents.id);
+  }
+
+  isEmpty() {
+    const {
+      sourceTree
+    } = this.state;
+    return sourceTree.contents.length === 0;
+  }
+
   renderItemName(name) {
     const hosts = {
       "ng://": "Angular",
       "webpack://": "Webpack",
       "moz-extension://": L10N.getStr("extensionsText")
     };
     return hosts[name] || name;
   }
 
   renderEmptyElement(message) {
     return _react2.default.createElement("div", {
+      key: "empty",
       className: "no-sources-message"
     }, message);
   }
 
-  render() {
+  renderProjectRootHeader() {
     const {
-      expanded,
       projectRoot
     } = this.props;
     const {
-      focusedItem,
-      highlightItems,
-      listItems,
-      parentMap,
       sourceTree
     } = this.state;
 
-    const onExpand = (item, expandedState) => {
-      this.props.setExpandedState(expandedState);
-    };
-
-    const onCollapse = (item, expandedState) => {
-      this.props.setExpandedState(expandedState);
-    };
-
-    const isEmpty = sourceTree.contents.length === 0;
-    const isCustomRoot = projectRoot !== "";
-
-    let roots = () => sourceTree.contents;
-
-    let clearProjectRootButton = null; // The "sourceTree.contents[0]" check ensures that there are contents
-    // A custom root with no existing sources will be ignored
-
-    if (isCustomRoot) {
-      const sourceContents = sourceTree.contents[0];
-      let rootLabel = projectRoot.split("/").pop();
+    if (!projectRoot) {
+      return null;
+    }
 
-      roots = () => sourceContents.contents;
-
-      if (sourceContents && sourceContents.name !== rootLabel) {
-        rootLabel = sourceContents.contents[0].name;
-
-        roots = () => sourceContents.contents[0].contents;
-      }
+    const sourceContents = sourceTree.contents[0];
+    let rootLabel = projectRoot.split("/").pop();
 
-      clearProjectRootButton = _react2.default.createElement("button", {
-        className: "sources-clear-root",
-        onClick: () => this.props.clearProjectDirectoryRoot(),
-        title: L10N.getStr("removeDirectoryRoot.label")
-      }, _react2.default.createElement(_Svg2.default, {
-        name: "home"
-      }), _react2.default.createElement(_Svg2.default, {
-        name: "breadcrumb",
-        "class": true
-      }), _react2.default.createElement("span", {
-        className: "sources-clear-root-label"
-      }, rootLabel));
+    if (sourceContents && sourceContents.name !== rootLabel) {
+      rootLabel = sourceContents.contents[0].name;
     }
 
-    if (isEmpty && !isCustomRoot) {
-      return this.renderEmptyElement(L10N.getStr("sources.noSourcesAvailable"));
-    }
+    return _react2.default.createElement("div", {
+      key: "root",
+      className: "sources-clear-root-container"
+    }, _react2.default.createElement("button", {
+      className: "sources-clear-root",
+      onClick: () => this.props.clearProjectDirectoryRoot(),
+      title: L10N.getStr("removeDirectoryRoot.label")
+    }, _react2.default.createElement(_Svg2.default, {
+      name: "home"
+    }), _react2.default.createElement(_Svg2.default, {
+      name: "breadcrumb",
+      "class": true
+    }), _react2.default.createElement("span", {
+      className: "sources-clear-root-label"
+    }, rootLabel)));
+  }
 
+  renderTree() {
+    const {
+      expanded
+    } = this.props;
+    const {
+      highlightItems,
+      listItems,
+      parentMap
+    } = this.state;
     const treeProps = {
       autoExpandAll: false,
       autoExpandDepth: expanded ? 0 : 1,
       expanded,
       getChildren: item => (0, _sourcesTree.nodeHasChildren)(item) ? item.contents : [],
       getParent: item => parentMap.get(item),
       getPath: this.getPath,
-      getRoots: roots,
+      getRoots: this.getRoots,
       highlightItems,
       itemHeight: 21,
-      key: isEmpty ? "empty" : "full",
+      key: this.isEmpty() ? "empty" : "full",
       listItems,
-      onCollapse,
-      onExpand,
+      onCollapse: this.onCollapse,
+      onExpand: this.onExpand,
       onFocus: this.focusItem,
       renderItem: this.renderItem
     };
-
-    const tree = _react2.default.createElement(_ManagedTree2.default, treeProps);
+    return _react2.default.createElement(_ManagedTree2.default, treeProps);
+  }
 
-    const onKeyDown = e => {
-      if (e.keyCode === 13 && focusedItem) {
-        this.selectItem(focusedItem);
-      }
-    };
-
+  renderPane(...children) {
+    const {
+      projectRoot
+    } = this.props;
     return _react2.default.createElement("div", {
+      key: "pane",
       className: (0, _classnames2.default)("sources-pane", {
-        "sources-list-custom-root": isCustomRoot
+        "sources-list-custom-root": projectRoot
       })
-    }, isCustomRoot ? _react2.default.createElement("div", {
-      className: "sources-clear-root-container"
-    }, clearProjectRootButton) : null, isEmpty ? this.renderEmptyElement(L10N.getStr("sources.noSourcesAvailableRoot")) : _react2.default.createElement("div", {
+    }, children);
+  }
+
+  render() {
+    const {
+      projectRoot
+    } = this.props;
+
+    if (this.isEmpty()) {
+      if (projectRoot) {
+        return this.renderPane(this.renderProjectRootHeader(), this.renderEmptyElement(L10N.getStr("sources.noSourcesAvailableRoot")));
+      }
+
+      return this.renderPane(this.renderEmptyElement(L10N.getStr("sources.noSourcesAvailable")));
+    }
+
+    return this.renderPane(this.renderProjectRootHeader(), _react2.default.createElement("div", {
+      key: "tree",
       className: "sources-list",
-      onKeyDown: onKeyDown
-    }, tree));
+      onKeyDown: this.onKeyDown
+    }, this.renderTree()));
   }
 
 }
 
 var _initialiseProps = function () {
   this.focusItem = item => {
     this.setState({
       focusedItem: item
     });
   };
 
   this.selectItem = item => {
-    if (!(0, _sourcesTree.nodeHasChildren)(item)) {
-      this.props.selectLocation({
-        sourceId: item.contents.get("id")
-      });
+    if (!(0, _sourcesTree.isDirectory)(item)) {
+      this.props.selectSource(item.contents.id);
     }
   };
 
   this.getPath = item => {
-    const {
-      sources
-    } = this.props;
-    const obj = item.contents.get && item.contents.get("id");
-    let blackBoxedPart = "";
+    const path = `${item.path}/${item.name}`;
 
-    if (typeof obj !== "undefined" && sources.has(obj) && sources.get(obj).get("isBlackBoxed")) {
-      blackBoxedPart = "update";
+    if ((0, _sourcesTree.isDirectory)(item)) {
+      return path;
     }
 
-    return `${item.path}/${item.name}/${blackBoxedPart}`;
+    const source = this.getSource(item);
+    const blackBoxedPart = source.isBlackBoxed ? ":blackboxed" : "";
+    return `${path}${blackBoxedPart}`;
   };
 
   this.getIcon = (sources, item, depth) => {
     const {
       debuggeeUrl,
       projectRoot
     } = this.props;
 
@@ -290,48 +299,45 @@ var _initialiseProps = function () {
     if (depth === 0 && projectRoot === "") {
       return _react2.default.createElement("img", {
         className: (0, _classnames2.default)("domain", {
           debuggee: debuggeeUrl && debuggeeUrl.includes(item.name)
         })
       });
     }
 
-    if (!(0, _sourcesTree.nodeHasChildren)(item)) {
-      const obj = item.contents.get("id");
-      const source = sources.get(obj);
-      const className = (0, _classnames2.default)((0, _source.getSourceClassnames)(source), "source-icon");
+    if ((0, _sourcesTree.isDirectory)(item)) {
       return _react2.default.createElement("img", {
-        className: className
+        className: "folder"
       });
     }
 
+    const source = this.getSource(item);
     return _react2.default.createElement("img", {
-      className: "folder"
+      className: (0, _classnames2.default)((0, _source.getSourceClassnames)(source), "source-icon")
     });
   };
 
   this.onContextMenu = (event, item) => {
     const copySourceUri2Label = L10N.getStr("copySourceUri2");
     const copySourceUri2Key = L10N.getStr("copySourceUri2.accesskey");
     const setDirectoryRootLabel = L10N.getStr("setDirectoryRoot.label");
     const setDirectoryRootKey = L10N.getStr("setDirectoryRoot.accesskey");
     const removeDirectoryRootLabel = L10N.getStr("removeDirectoryRoot.label");
     event.stopPropagation();
     event.preventDefault();
     const menuOptions = [];
 
     if (!(0, _sourcesTree.isDirectory)(item)) {
-      const source = item.contents.get("url");
       const copySourceUri2 = {
         id: "node-menu-copy-source",
         label: copySourceUri2Label,
         accesskey: copySourceUri2Key,
         disabled: false,
-        click: () => (0, _clipboard.copyToTheClipboard)(source)
+        click: () => (0, _clipboard.copyToTheClipboard)(item.contents.url)
       };
       menuOptions.push(copySourceUri2);
     }
 
     if ((0, _sourcesTree.isDirectory)(item) && _prefs.features.root) {
       const {
         path
       } = item;
@@ -355,16 +361,34 @@ var _initialiseProps = function () {
           click: () => this.props.setProjectDirectoryRoot(path)
         });
       }
     }
 
     (0, _devtoolsContextmenu.showMenu)(event, menuOptions);
   };
 
+  this.onExpand = (item, expandedState) => {
+    this.props.setExpandedState(expandedState);
+  };
+
+  this.onCollapse = (item, expandedState) => {
+    this.props.setExpandedState(expandedState);
+  };
+
+  this.onKeyDown = e => {
+    const {
+      focusedItem
+    } = this.state;
+
+    if (e.keyCode === 13 && focusedItem) {
+      this.selectItem(focusedItem);
+    }
+  };
+
   this.renderItem = (item, depth, focused, _, expanded, {
     setExpanded
   }) => {
     const arrow = (0, _sourcesTree.nodeHasChildren)(item) ? _react2.default.createElement("img", {
       className: (0, _classnames2.default)("arrow", {
         expanded: expanded
       })
     }) : _react2.default.createElement("i", {
@@ -388,28 +412,50 @@ var _initialiseProps = function () {
           this.selectItem(item);
         }
       },
       onContextMenu: e => this.onContextMenu(e, item)
     }, arrow, icon, _react2.default.createElement("span", {
       className: "label"
     }, " ", this.renderItemName(item.name), " "));
   };
+
+  this.getRoots = () => {
+    const {
+      projectRoot
+    } = this.props;
+    const {
+      sourceTree
+    } = this.state;
+    const sourceContents = sourceTree.contents[0];
+    const rootLabel = projectRoot.split("/").pop(); // The "sourceTree.contents[0]" check ensures that there are contents
+    // A custom root with no existing sources will be ignored
+
+    if (projectRoot) {
+      if (sourceContents && sourceContents.name !== rootLabel) {
+        return sourceContents.contents[0].contents;
+      }
+
+      return sourceContents.contents;
+    }
+
+    return sourceTree.contents;
+  };
 };
 
 const mapStateToProps = state => {
   return {
     shownSource: (0, _selectors.getShownSource)(state),
     selectedSource: (0, _selectors.getSelectedSource)(state),
     debuggeeUrl: (0, _selectors.getDebuggeeUrl)(state),
     expanded: (0, _selectors.getExpandedState)(state),
     projectRoot: (0, _selectors.getProjectDirectoryRoot)(state),
     sources: (0, _selectors.getSources)(state)
   };
 };
 
 const actionCreators = {
   setExpandedState: _sourceTree.setExpandedState,
-  selectLocation: _sources.selectLocation,
+  selectSource: _sources.selectSource,
   setProjectDirectoryRoot: _ui.setProjectDirectoryRoot,
   clearProjectDirectoryRoot: _ui.clearProjectDirectoryRoot
 };
 exports.default = (0, _reactRedux.connect)(mapStateToProps, actionCreators)(SourcesTree);
\ No newline at end of file

--- a/devtools/client/debugger/new/src/utils/editor/source-documents.js
+++ b/devtools/client/debugger/new/src/utils/editor/source-documents.js
@@ -1,14 +1,24 @@
 "use strict";
 
 Object.defineProperty(exports, "__esModule", {
   value: true
 });
-exports.showLoading = exports.showErrorMessage = exports.showSourceText = exports.clearEditor = exports.updateDocument = exports.updateLineNumberFormat = exports.clearDocuments = exports.removeDocument = exports.hasDocument = exports.setDocument = exports.getDocument = undefined;
+exports.getDocument = getDocument;
+exports.hasDocument = hasDocument;
+exports.setDocument = setDocument;
+exports.removeDocument = removeDocument;
+exports.clearDocuments = clearDocuments;
+exports.updateLineNumberFormat = updateLineNumberFormat;
+exports.updateDocument = updateDocument;
+exports.clearEditor = clearEditor;
+exports.showLoading = showLoading;
+exports.showErrorMessage = showErrorMessage;
+exports.showSourceText = showSourceText;
 
 var _source = require("../source");
 
 var _wasm = require("../wasm");
 
 var _ui = require("../ui");
 
 var _sourceEditor = require("devtools/client/sourceeditor/editor");
@@ -163,21 +173,9 @@ function showSourceText(editor, source, 
   }
 
   const doc = editor.createDocument();
   setDocument(source.id, doc);
   editor.replaceDocument(doc);
   setEditorText(editor, source);
   editor.setMode((0, _source.getMode)(source, symbols));
   updateLineNumberFormat(editor, source.id);
-}
-
-exports.getDocument = getDocument;
-exports.setDocument = setDocument;
-exports.hasDocument = hasDocument;
-exports.removeDocument = removeDocument;
-exports.clearDocuments = clearDocuments;
-exports.updateLineNumberFormat = updateLineNumberFormat;
-exports.updateDocument = updateDocument;
-exports.clearEditor = clearEditor;
-exports.showSourceText = showSourceText;
-exports.showErrorMessage = showErrorMessage;
-exports.showLoading = showLoading;
\ No newline at end of file
+}
\ No newline at end of file

--- a/devtools/client/debugger/new/src/utils/path.js
+++ b/devtools/client/debugger/new/src/utils/path.js
@@ -1,13 +1,18 @@
 "use strict";
 
 Object.defineProperty(exports, "__esModule", {
   value: true
 });
+exports.basename = basename;
+exports.dirname = dirname;
+exports.isURL = isURL;
+exports.isAbsolute = isAbsolute;
+exports.join = join;
 
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at <http://mozilla.org/MPL/2.0/>. */
 function basename(path) {
   return path.split("/").pop();
 }
 
@@ -21,15 +26,9 @@ function isURL(str) {
 }
 
 function isAbsolute(str) {
   return str[0] === "/";
 }
 
 function join(base, dir) {
   return `${base}/${dir}`;
-}
-
-exports.basename = basename;
-exports.dirname = dirname;
-exports.isURL = isURL;
-exports.isAbsolute = isAbsolute;
-exports.join = join;
\ No newline at end of file
+}
\ No newline at end of file

--- a/devtools/client/debugger/new/src/utils/result-list.js
+++ b/devtools/client/debugger/new/src/utils/result-list.js
@@ -1,14 +1,14 @@
 "use strict";
 
 Object.defineProperty(exports, "__esModule", {
   value: true
 });
-exports.scrollList = undefined;
+exports.scrollList = scrollList;
 
 var _devtoolsEnvironment = require("devtools/client/debugger/new/dist/vendors").vendored["devtools-environment"];
 
 var _Modal = require("../components/shared/Modal");
 
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at <http://mozilla.org/MPL/2.0/>. */
@@ -48,11 +48,9 @@ function chromeScrollList(elem, index) {
 
   const resultsHeight = resultsEl.clientHeight;
   const itemHeight = resultsEl.children[0].clientHeight;
   const numVisible = resultsHeight / itemHeight;
   const positionsToScroll = index - numVisible + 1;
   const itemOffset = resultsHeight % itemHeight;
   const scroll = positionsToScroll * (itemHeight + 2) + itemOffset;
   resultsEl.scrollTop = Math.max(0, scroll);
-}
-
-exports.scrollList = scrollList;
\ No newline at end of file
+}
\ No newline at end of file

--- a/devtools/client/debugger/new/src/utils/source.js
+++ b/devtools/client/debugger/new/src/utils/source.js
@@ -421,27 +421,22 @@ function isLoaded(source) {
   return source.get("loadedState") === "loaded";
 }
 
 function isLoading(source) {
   return source.get("loadedState") === "loading";
 }
 
 function getTextAtPosition(source, location) {
-  if (!source || !source.text) {
+  if (!source || !source.text || source.isWasm) {
     return "";
   }
 
   const line = location.line;
   const column = location.column || 0;
-
-  if (source.isWasm) {
-    return "";
-  }
-
   const lineText = source.text.split("\n")[line - 1];
 
   if (!lineText) {
     return "";
   }
 
   return lineText.slice(column, column + 100).trim();
 }
@@ -461,10 +456,10 @@ function getSourceClassnames(source, sou
   if (isPretty(source)) {
     return "prettyPrint";
   }
 
   if (source.isBlackBoxed) {
     return "blackBox";
   }
 
-  return sourceTypes[(0, _sourcesTree.getExtension)(source.url)] || defaultClassName;
+  return sourceTypes[(0, _sourcesTree.getFileExtension)(source.url)] || defaultClassName;
 }
\ No newline at end of file

--- a/devtools/client/debugger/new/src/utils/sources-tree/addToTree.js
+++ b/devtools/client/debugger/new/src/utils/sources-tree/addToTree.js
@@ -124,17 +124,17 @@ function addSourceToNode(node, url, sour
 }
 /**
  * @memberof utils/sources-tree
  * @static
  */
 
 
 function addToTree(tree, source, debuggeeUrl, projectRoot) {
-  const url = (0, _getURL.getURL)(source.get("url"), debuggeeUrl);
+  const url = (0, _getURL.getURL)(source.get ? source.get("url") : source.url, debuggeeUrl);
   const debuggeeHost = (0, _treeOrder.getDomain)(debuggeeUrl);
 
   if ((0, _utils.isInvalidUrl)(url, source) || !isUnderRoot(url, projectRoot)) {
     return;
   }
 
   const finalNode = traverseTree(url, tree, debuggeeHost, projectRoot);
   finalNode.contents = addSourceToNode(finalNode, url, source);

--- a/devtools/client/debugger/new/src/utils/sources-tree/index.js
+++ b/devtools/client/debugger/new/src/utils/sources-tree/index.js
@@ -97,16 +97,22 @@ Object.defineProperty(exports, "createNo
   }
 });
 Object.defineProperty(exports, "createParentMap", {
   enumerable: true,
   get: function () {
     return _utils.createParentMap;
   }
 });
+Object.defineProperty(exports, "getFileExtension", {
+  enumerable: true,
+  get: function () {
+    return _utils.getFileExtension;
+  }
+});
 Object.defineProperty(exports, "getRelativePath", {
   enumerable: true,
   get: function () {
     return _utils.getRelativePath;
   }
 });
 Object.defineProperty(exports, "isDirectory", {
   enumerable: true,
@@ -126,15 +132,9 @@ Object.defineProperty(exports, "isNotJav
     return _utils.isNotJavaScript;
   }
 });
 Object.defineProperty(exports, "nodeHasChildren", {
   enumerable: true,
   get: function () {
     return _utils.nodeHasChildren;
   }
-});
-Object.defineProperty(exports, "getExtension", {
-  enumerable: true,
-  get: function () {
-    return _utils.getExtension;
-  }
 });
\ No newline at end of file

--- a/devtools/client/debugger/new/src/utils/sources-tree/utils.js
+++ b/devtools/client/debugger/new/src/utils/sources-tree/utils.js
@@ -1,17 +1,17 @@
 "use strict";
 
 Object.defineProperty(exports, "__esModule", {
   value: true
 });
 exports.nodeHasChildren = nodeHasChildren;
 exports.isExactUrlMatch = isExactUrlMatch;
 exports.isDirectory = isDirectory;
-exports.getExtension = getExtension;
+exports.getFileExtension = getFileExtension;
 exports.isNotJavaScript = isNotJavaScript;
 exports.isInvalidUrl = isInvalidUrl;
 exports.partIsFile = partIsFile;
 exports.createNode = createNode;
 exports.createParentMap = createParentMap;
 exports.getRelativePath = getRelativePath;
 
 var _url = require("devtools/client/debugger/new/dist/vendors").vendored["url"];
@@ -42,32 +42,32 @@ function isExactUrlMatch(pathPart, debug
 
 function isDirectory(url) {
   const parts = url.path.split("/").filter(p => p !== ""); // Assume that all urls point to files except when they end with '/'
   // Or directory node has children
 
   return (parts.length === 0 || url.path.slice(-1) === "/" || nodeHasChildren(url)) && url.name != "(index)";
 }
 
-function getExtension(url = "") {
+function getFileExtension(url = "") {
   const parsedUrl = (0, _url.parse)(url).pathname;
 
   if (!parsedUrl) {
     return "";
   }
 
   return parsedUrl.split(".").pop();
 }
 
 function isNotJavaScript(source) {
-  return ["css", "svg", "png"].includes(getExtension(source.url));
+  return ["css", "svg", "png"].includes(getFileExtension(source.url));
 }
 
 function isInvalidUrl(url, source) {
-  return IGNORED_URLS.indexOf(url) != -1 || !source.get("url") || !url.group || (0, _source.isPretty)(source) || isNotJavaScript(source);
+  return IGNORED_URLS.indexOf(url) != -1 || !(source.get ? source.get("url") : source.url) || !url.group || (0, _source.isPretty)(source) || isNotJavaScript(source);
 }
 
 function partIsFile(index, parts, url) {
   const isLastPart = index === parts.length - 1;
   return !isDirectory(url) && isLastPart;
 }
 
 function createNode(name, path, contents) {

--- a/devtools/client/debugger/new/src/utils/task.js
+++ b/devtools/client/debugger/new/src/utils/task.js
@@ -10,17 +10,17 @@ Object.defineProperty(exports, "__esModu
 
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at <http://mozilla.org/MPL/2.0/>. */
 
 /**
  * This object provides the public module functions.
  */
-const Task = {
+const Task = exports.Task = {
   // XXX: Not sure if this works in all cases...
   async: function (task) {
     return function () {
       return Task.spawn(task, this, arguments);
     };
   },
 
   /**
@@ -44,10 +44,9 @@ const Task = {
           reject(error);
           iterator.throw(error);
         });
       };
 
       callNext(undefined);
     });
   }
-};
-exports.Task = Task;
\ No newline at end of file
+};
\ No newline at end of file

--- a/devtools/client/debugger/new/src/utils/text.js
+++ b/devtools/client/debugger/new/src/utils/text.js
@@ -1,14 +1,15 @@
 "use strict";
 
 Object.defineProperty(exports, "__esModule", {
   value: true
 });
-exports.truncateMiddleText = exports.formatKeyShortcut = undefined;
+exports.formatKeyShortcut = formatKeyShortcut;
+exports.truncateMiddleText = truncateMiddleText;
 
 var _devtoolsModules = require("devtools/client/debugger/new/dist/vendors").vendored["devtools-modules"];
 
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at <http://mozilla.org/MPL/2.0/>. */
 
 /**
@@ -54,12 +55,9 @@ function formatKeyShortcut(shortcut) {
 function truncateMiddleText(sourceText, maxLength) {
   let truncatedText = sourceText;
 
   if (sourceText.length > maxLength) {
     truncatedText = `${sourceText.substring(0, Math.round(maxLength / 2) - 2)}...${sourceText.substring(sourceText.length - Math.round(maxLength / 2 - 1))}`;
   }
 
   return truncatedText;
-}
-
-exports.formatKeyShortcut = formatKeyShortcut;
-exports.truncateMiddleText = truncateMiddleText;
\ No newline at end of file
+}
\ No newline at end of file

--- a/devtools/client/debugger/new/src/utils/utils.js
+++ b/devtools/client/debugger/new/src/utils/utils.js
@@ -1,13 +1,17 @@
 "use strict";
 
 Object.defineProperty(exports, "__esModule", {
   value: true
 });
+exports.handleError = handleError;
+exports.promisify = promisify;
+exports.endTruncateStr = endTruncateStr;
+exports.waitForMs = waitForMs;
 
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at <http://mozilla.org/MPL/2.0/>. */
 
 /**
  * Utils for utils, by utils
  * @module utils/utils
@@ -49,14 +53,9 @@ function endTruncateStr(str, size) {
     return `...${str.slice(str.length - size)}`;
   }
 
   return str;
 }
 
 function waitForMs(ms) {
   return new Promise(resolve => setTimeout(resolve, ms));
-}
-
-exports.handleError = handleError;
-exports.promisify = promisify;
-exports.endTruncateStr = endTruncateStr;
-exports.waitForMs = waitForMs;
\ No newline at end of file
+}
\ No newline at end of file

--- a/devtools/client/debugger/new/src/utils/wasm.js
+++ b/devtools/client/debugger/new/src/utils/wasm.js
@@ -1,14 +1,20 @@
 "use strict";
 
 Object.defineProperty(exports, "__esModule", {
   value: true
 });
-exports.renderWasmText = exports.clearWasmStates = exports.wasmOffsetToLine = exports.lineToWasmOffset = exports.isWasm = exports.getWasmLineNumberFormatter = exports.getWasmText = undefined;
+exports.getWasmText = getWasmText;
+exports.getWasmLineNumberFormatter = getWasmLineNumberFormatter;
+exports.isWasm = isWasm;
+exports.lineToWasmOffset = lineToWasmOffset;
+exports.wasmOffsetToLine = wasmOffsetToLine;
+exports.clearWasmStates = clearWasmStates;
+exports.renderWasmText = renderWasmText;
 
 var _WasmParser = require("devtools/client/shared/vendor/WasmParser");
 
 var _WasmDis = require("devtools/client/shared/vendor/WasmDis");
 
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at <http://mozilla.org/MPL/2.0/>. */
@@ -174,17 +180,9 @@ function renderWasmText(sourceId, {
   const MAX_LINES = 1000000;
 
   if (lines.length > MAX_LINES) {
     lines.splice(MAX_LINES, lines.length - MAX_LINES);
     lines.push(";; .... text is truncated due to the size");
   }
 
   return lines;
-}
-
-exports.getWasmText = getWasmText;
-exports.getWasmLineNumberFormatter = getWasmLineNumberFormatter;
-exports.isWasm = isWasm;
-exports.lineToWasmOffset = lineToWasmOffset;
-exports.wasmOffsetToLine = wasmOffsetToLine;
-exports.clearWasmStates = clearWasmStates;
-exports.renderWasmText = renderWasmText;
\ No newline at end of file
+}
\ No newline at end of file

--- a/devtools/client/debugger/new/src/workers/parser/utils/helpers.js
+++ b/devtools/client/debugger/new/src/workers/parser/utils/helpers.js
@@ -51,17 +51,17 @@ function isYieldExpression(path) {
   const {
     node,
     parent
   } = path;
   return t.isYieldExpression(node) || t.isYieldExpression(parent.init) || t.isYieldExpression(parent);
 }
 
 function isObjectShorthand(parent) {
-  return t.isObjectProperty(parent) && parent.key.start == parent.value.start && parent.key.loc.identifierName === parent.value.loc.identifierName;
+  return t.isObjectProperty(parent) && parent.value && parent.key.start == parent.value.start && parent.key.loc.identifierName === parent.value.loc.identifierName;
 }
 
 function getObjectExpressionValue(node) {
   const {
     value
   } = node;
 
   if (t.isIdentifier(value)) {

--- a/devtools/client/shared/components/reps/reps.css
+++ b/devtools/client/shared/components/reps/reps.css
@@ -221,16 +221,20 @@ html[dir="rtl"] .tree-node img.arrow {
   color: var(--string-color);
   border-width: 1px;
   border-style: solid;
   border-radius: 2px;
   font-size: 0.8em;
   padding: 0 2px;
 }
 
+.objectBox-node.clickable {
+  cursor: pointer;
+}
+
 /******************************************************************************/
 
 .objectBox-event,
 .objectBox-eventLog,
 .objectBox-regexp,
 .objectBox-object {
   color: var(--object-color);
   white-space: pre-wrap;
@@ -327,16 +331,17 @@ html[dir="rtl"] .tree-node img.arrow {
 
 button.open-inspector {
   mask: url("chrome://devtools/skin/images/devtools-reps/open-inspector.svg") no-repeat;
   display: inline-block;
   background-color: var(--comment-node-color);
   height: 16px;
   margin-left: 0.25em;
   vertical-align: middle;
+  cursor: pointer;
 }
 
 .objectBox-node:hover .open-inspector,
 .objectBox-textNode:hover .open-inspector,
 .open-inspector:hover {
   background-color: var(--theme-highlight-blue);
 }
 

--- a/devtools/client/shared/components/reps/reps.js
+++ b/devtools/client/shared/components/reps/reps.js
@@ -5675,17 +5675,18 @@ function ElementNode(props) {
   const baseConfig = {
     "data-link-actor-id": object.actor,
     className: "objectBox objectBox-node"
   };
   let inspectIcon;
   if (isInTree) {
     if (onDOMNodeClick) {
       Object.assign(baseConfig, {
-        onClick: _ => onDOMNodeClick(object)
+        onClick: _ => onDOMNodeClick(object),
+        className: `${baseConfig.className} clickable`
       });
     }
 
     if (onDOMNodeMouseOver) {
       Object.assign(baseConfig, {
         onMouseOver: _ => onDOMNodeMouseOver(object)
       });
     }

--- a/devtools/server/actors/accessibility.js
+++ b/devtools/server/actors/accessibility.js
@@ -498,18 +498,25 @@ const AccessibleWalkerActor = ActorClass
       this.refMap.clear();
     }
   },
 
   /**
    * A helper method. Accessibility walker is assumed to have only 1 child which
    * is the top level document.
    */
-  children() {
-    return Promise.all([this.getDocument()]);
+  async children() {
+    if (this._childrenPromise) {
+      return this._childrenPromise;
+    }
+
+    this._childrenPromise = Promise.all([this.getDocument()]);
+    let children = await this._childrenPromise;
+    this._childrenPromise = null;
+    return children;
   },
 
   /**
    * A promise for a root document accessible actor that only resolves when its
    * corresponding document accessible object is fully loaded.
    *
    * @return {Promise}
    */

--- a/docshell/base/nsPingListener.cpp
+++ b/docshell/base/nsPingListener.cpp
@@ -157,17 +157,17 @@ SendPing(void* aClosure, nsIContent* aCo
     MOZ_ASSERT(NS_SUCCEEDED(rv));
   }
 
   nsCOMPtr<nsIScriptSecurityManager> sm =
     do_GetService(NS_SCRIPTSECURITYMANAGER_CONTRACTID);
 
   if (sm && info->referrer) {
     bool referrerIsSecure;
-    uint32_t flags = nsIProtocolHandler::URI_SAFE_TO_LOAD_IN_SECURE_CONTEXT;
+    uint32_t flags = nsIProtocolHandler::URI_IS_POTENTIALLY_TRUSTWORTHY;
     rv = NS_URIChainHasFlags(info->referrer, flags, &referrerIsSecure);
 
     // Default to sending less data if NS_URIChainHasFlags() fails.
     referrerIsSecure = NS_FAILED(rv) || referrerIsSecure;
 
     bool sameOrigin =
       NS_SUCCEEDED(sm->CheckSameOriginURI(info->referrer, aURI, false));
 

--- a/dom/base/DocGroup.cpp
+++ b/dom/base/DocGroup.cpp
@@ -179,10 +179,22 @@ DocGroup::MoveSignalSlotListTo(nsTArray<
   aDest.SetCapacity(aDest.Length() + mSignalSlotList.Length());
   for (RefPtr<HTMLSlotElement>& slot : mSignalSlotList) {
     slot->RemovedFromSignalSlotList();
     aDest.AppendElement(Move(slot));
   }
   mSignalSlotList.Clear();
 }
 
+bool
+DocGroup::IsActive() const
+{
+  for (nsIDocument* doc : mDocuments) {
+    if (doc->IsCurrentActiveDocument()) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
 }
 }

--- a/dom/base/DocGroup.h
+++ b/dom/base/DocGroup.h
@@ -117,16 +117,19 @@ public:
   // microtask.
   void SignalSlotChange(HTMLSlotElement& aSlot);
 
   void MoveSignalSlotListTo(nsTArray<RefPtr<HTMLSlotElement>>& aDest);
 
   // List of DocGroups that has non-empty signal slot list.
   static AutoTArray<RefPtr<DocGroup>, 2>* sPendingDocGroups;
 
+  // Returns true if any of its documents are active but not in the bfcache.
+  bool IsActive() const;
+
 private:
   DocGroup(TabGroup* aTabGroup, const nsACString& aKey);
   ~DocGroup();
 
   nsCString mKey;
   RefPtr<TabGroup> mTabGroup;
   nsTArray<nsIDocument*> mDocuments;
   RefPtr<mozilla::dom::CustomElementReactionsStack> mReactionsStack;

--- a/dom/base/TabGroup.cpp
+++ b/dom/base/TabGroup.cpp
@@ -301,10 +301,27 @@ TabGroup::IsBackground() const
     }
   }
   MOZ_ASSERT(foregrounded == mForegroundCount);
 #endif
 
   return mForegroundCount == 0;
 }
 
+uint32_t
+TabGroup::Count(bool aActiveOnly) const
+{
+  if (!aActiveOnly) {
+    return mDocGroups.Count();
+  }
+
+  uint32_t count = 0;
+  for (auto iter = mDocGroups.ConstIter(); !iter.Done(); iter.Next()) {
+    if (iter.Get()->mDocGroup->IsActive()) {
+      ++count;
+    }
+  }
+
+  return count;
+}
+
 } // namespace dom
 } // namespace mozilla

--- a/dom/base/TabGroup.h
+++ b/dom/base/TabGroup.h
@@ -95,16 +95,20 @@ public:
 
   void Leave(nsPIDOMWindowOuter* aWindow);
 
   Iterator Iter()
   {
     return mDocGroups.Iter();
   }
 
+  // Returns the size of the set of "similar-origin" DocGroups. To
+  // only consider DocGroups with at least one active document, call
+  // Count with 'aActiveOnly' = true
+  uint32_t Count(bool aActiveOnly = false) const;
 
   // Returns the nsIDocShellTreeItem with the given name, searching each of the
   // docShell trees which are within this TabGroup. It will pass itself as
   // aRequestor to each docShellTreeItem which it asks to search for the name,
   // and will not search the docShellTreeItem which is passed as aRequestor.
   //
   // This method is used in order to correctly namespace named windows based on
   // their unit of related browsing contexts.

--- a/dom/base/nsContentUtils.cpp
+++ b/dom/base/nsContentUtils.cpp
@@ -167,17 +167,16 @@
 #include "nsIScriptError.h"
 #include "nsIScriptGlobalObject.h"
 #include "nsIScriptObjectPrincipal.h"
 #include "nsIScriptSecurityManager.h"
 #include "nsIScrollable.h"
 #include "nsIStreamConverterService.h"
 #include "nsIStringBundle.h"
 #include "nsIURI.h"
-#include "nsIURIWithPrincipal.h"
 #include "nsIURL.h"
 #include "nsIWebNavigation.h"
 #include "nsIWindowMediator.h"
 #include "nsIXPConnect.h"
 #include "nsJSUtils.h"
 #include "nsMappedAttributes.h"
 #include "nsNetCID.h"
 #include "nsNetUtil.h"
@@ -3080,39 +3079,39 @@ nsContentUtils::GenerateStateKey(nsICont
 
 // static
 nsIPrincipal*
 nsContentUtils::SubjectPrincipal(JSContext* aCx)
 {
   MOZ_ASSERT(NS_IsMainThread());
 
   // As opposed to SubjectPrincipal(), we do in fact assume that
-  // we're in a compartment here; anyone who calls this function
-  // in situations where that's not the case is doing it wrong.
-  JSCompartment* compartment = js::GetContextCompartment(aCx);
-  MOZ_ASSERT(compartment);
-
-  JSPrincipals* principals = JS_GetCompartmentPrincipals(compartment);
+  // we're in a realm here; anyone who calls this function in
+  // situations where that's not the case is doing it wrong.
+  JS::Realm* realm = js::GetContextRealm(aCx);
+  MOZ_ASSERT(realm);
+
+  JSPrincipals* principals = JS::GetRealmPrincipals(realm);
   return nsJSPrincipals::get(principals);
 }
 
 // static
 nsIPrincipal*
 nsContentUtils::SubjectPrincipal()
 {
   MOZ_ASSERT(IsInitialized());
   MOZ_ASSERT(NS_IsMainThread());
   JSContext* cx = GetCurrentJSContext();
   if (!cx) {
     MOZ_CRASH("Accessing the Subject Principal without an AutoJSAPI on the stack is forbidden");
   }
 
-  JSCompartment *compartment = js::GetContextCompartment(cx);
-
-  // When an AutoJSAPI is instantiated, we are in a null compartment until the
+  JS::Realm* realm = js::GetContextRealm(cx);
+
+  // When an AutoJSAPI is instantiated, we are in a null realm until the
   // first JSAutoRealm, which is kind of a purgatory as far as permissions
   // go. It would be nice to just hard-abort if somebody does a security check
   // in this purgatory zone, but that would be too fragile, since it could be
   // triggered by random IsCallerChrome() checks 20-levels deep.
   //
   // So we want to return _something_ here - and definitely not the System
   // Principal, since that would make an AutoJSAPI a very dangerous thing to
   // instantiate.
@@ -3120,19 +3119,19 @@ nsContentUtils::SubjectPrincipal()
   // The natural thing to return is a null principal. Ideally, we'd return a
   // different null principal each time, to avoid any unexpected interactions
   // when the principal accidentally gets inherited somewhere. But
   // SubjectPrincipal doesn't return strong references, so there's no way to
   // sanely manage the lifetime of multiple null principals.
   //
   // So we use a singleton null principal. To avoid it being accidentally
   // inherited and becoming a "real" subject or object principal, we do a
-  // release-mode assert during compartment creation against using this
-  // principal on an actual global.
-  if (!compartment) {
+  // release-mode assert during realm creation against using this principal on
+  // an actual global.
+  if (!realm) {
     return sNullSubjectPrincipal;
   }
 
   return SubjectPrincipal(cx);
 }
 
 // static
 nsIPrincipal*
@@ -6280,40 +6279,43 @@ nsContentUtils::GetASCIIOrigin(nsIPrinci
 }
 
 /* static */
 nsresult
 nsContentUtils::GetASCIIOrigin(nsIURI* aURI, nsACString& aOrigin)
 {
   MOZ_ASSERT(aURI, "missing uri");
 
-  // For Blob URI we have to return the origin of page using its principal.
-  nsCOMPtr<nsIURIWithPrincipal> uriWithPrincipal = do_QueryInterface(aURI);
-  if (uriWithPrincipal) {
-    nsCOMPtr<nsIPrincipal> principal;
-    uriWithPrincipal->GetPrincipal(getter_AddRefs(principal));
-
-    if (principal) {
-      nsCOMPtr<nsIURI> uri;
-      nsresult rv = principal->GetURI(getter_AddRefs(uri));
-      NS_ENSURE_SUCCESS(rv, rv);
-
-      if (uri && uri != aURI) {
-        return GetASCIIOrigin(uri, aOrigin);
-      }
-    }
+  bool isBlobURL = false;
+  nsresult rv = aURI->SchemeIs(BLOBURI_SCHEME, &isBlobURL);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // For Blob URI, the path is the URL of the owning page.
+  if (isBlobURL) {
+    nsAutoCString path;
+    rv = aURI->GetPathQueryRef(path);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    nsCOMPtr<nsIURI> uri;
+    nsresult rv = NS_NewURI(getter_AddRefs(uri), path);
+    if (NS_FAILED(rv)) {
+      aOrigin.AssignLiteral("null");
+      return NS_OK;
+    }
+
+    return GetASCIIOrigin(uri, aOrigin);
   }
 
   aOrigin.Truncate();
 
   nsCOMPtr<nsIURI> uri = NS_GetInnermostURI(aURI);
   NS_ENSURE_TRUE(uri, NS_ERROR_UNEXPECTED);
 
   nsCString host;
-  nsresult rv = uri->GetAsciiHost(host);
+  rv = uri->GetAsciiHost(host);
 
   if (NS_SUCCEEDED(rv) && !host.IsEmpty()) {
     nsCString scheme;
     rv = uri->GetScheme(scheme);
     NS_ENSURE_SUCCESS(rv, rv);
 
     int32_t port = -1;
     uri->GetPort(&port);

--- a/dom/base/nsDocument.cpp
+++ b/dom/base/nsDocument.cpp
@@ -2359,19 +2359,19 @@ nsIDocument::ResetToURI(nsIURI* aURI,
       }
     }
   }
 
   if (mFontFaceSet) {
     mFontFaceSet->RefreshStandardFontLoadPrincipal();
   }
 
-  // Refresh the principal on the compartment.
+  // Refresh the principal on the realm.
   if (nsPIDOMWindowInner* win = GetInnerWindow()) {
-    nsGlobalWindowInner::Cast(win)->RefreshCompartmentPrincipal();
+    nsGlobalWindowInner::Cast(win)->RefreshRealmPrincipal();
   }
 }
 
 already_AddRefed<nsIPrincipal>
 nsIDocument::MaybeDowngradePrincipal(nsIPrincipal* aPrincipal)
 {
   if (!aPrincipal) {
     return nullptr;
@@ -8490,16 +8490,28 @@ DispatchFullScreenChange(nsIDocument* aT
     /* Bubbles */ true, /* OnlyChrome */ false);
 }
 
 static void ClearPendingFullscreenRequests(nsIDocument* aDoc);
 
 void
 nsIDocument::OnPageHide(bool aPersisted, EventTarget* aDispatchStartTarget)
 {
+  if (mDocGroup && Telemetry::CanRecordExtended() &&
+      IsTopLevelContentDocument()) {
+    TabGroup* tabGroup = mDocGroup->GetTabGroup();
+
+    if (tabGroup) {
+      Telemetry::Accumulate(Telemetry::ACTIVE_DOCGROUPS_PER_TABGROUP,
+                            tabGroup->Count(true /* aActiveOnly */));
+      Telemetry::Accumulate(Telemetry::TOTAL_DOCGROUPS_PER_TABGROUP,
+                            tabGroup->Count());
+    }
+  }
+
   // Send out notifications that our <link> elements are detached,
   // but only if this is not a full unload.
   Element* root = GetRootElement();
   if (aPersisted && root) {
     RefPtr<nsContentList> links = NS_GetContentList(root,
                                                     kNameSpaceID_XHTML,
                                                     NS_LITERAL_STRING("link"));
 

--- a/dom/base/nsGlobalWindowInner.cpp
+++ b/dom/base/nsGlobalWindowInner.cpp
@@ -3627,20 +3627,20 @@ nsGlobalWindowInner::GetChildWindow(cons
 {
   if (GetOuterWindowInternal()) {
     return GetOuterWindowInternal()->GetChildWindow(aName);
   }
   return nullptr;
 }
 
 void
-nsGlobalWindowInner::RefreshCompartmentPrincipal()
-{
-  JS_SetCompartmentPrincipals(js::GetObjectCompartment(GetWrapperPreserveColor()),
-                              nsJSPrincipals::get(mDoc->NodePrincipal()));
+nsGlobalWindowInner::RefreshRealmPrincipal()
+{
+  JS::SetRealmPrincipals(js::GetNonCCWObjectRealm(GetWrapperPreserveColor()),
+                         nsJSPrincipals::get(mDoc->NodePrincipal()));
 }
 
 already_AddRefed<nsIWidget>
 nsGlobalWindowInner::GetMainWidget()
 {
   FORWARD_TO_OUTER(GetMainWidget, (), nullptr);
 }
 

--- a/dom/base/nsGlobalWindowInner.h
+++ b/dom/base/nsGlobalWindowInner.h
@@ -372,17 +372,17 @@ public:
                                   bool aForceReuseInnerWindow) override;
 
   virtual void SetOpenerWindow(nsPIDOMWindowOuter* aOpener,
                                bool aOriginalOpener) override;
 
   virtual void MaybeUpdateTouchState() override;
 
   // Inner windows only.
-  void RefreshCompartmentPrincipal();
+  void RefreshRealmPrincipal();
 
   // For accessing protected field mFullScreen
   friend class FullscreenTransitionTask;
 
   // Inner windows only.
   virtual void SetHasGamepadEventListener(bool aHasGamepad = true) override;
   void NotifyVREventListenerAdded();
   bool HasUsedVR() const;

--- a/dom/base/nsGlobalWindowOuter.cpp
+++ b/dom/base/nsGlobalWindowOuter.cpp
@@ -1742,34 +1742,36 @@ nsGlobalWindowOuter::SetNewDocument(nsID
     // so all expandos and such defined on the outer window should go away. Force
     // all Xray wrappers to be recomputed.
     JS::Rooted<JSObject*> rootedObject(cx, GetWrapper());
     if (!JS_RefreshCrossCompartmentWrappers(cx, rootedObject)) {
       return NS_ERROR_FAILURE;
     }
 
     // Inner windows are only reused for same-origin principals, but the principals
-    // don't necessarily match exactly. Update the principal on the compartment to
-    // match the new document.
-    // NB: We don't just call currentInner->RefreshCompartmentPrincipals() here
+    // don't necessarily match exactly. Update the principal on the realm to match
+    // the new document.
+    // NB: We don't just call currentInner->RefreshRealmPrincipals() here
     // because we haven't yet set its mDoc to aDocument.
-    JSCompartment *compartment = js::GetObjectCompartment(newInnerGlobal);
+    JS::Realm* realm = js::GetNonCCWObjectRealm(newInnerGlobal);
 #ifdef DEBUG
     bool sameOrigin = false;
     nsIPrincipal *existing =
-      nsJSPrincipals::get(JS_GetCompartmentPrincipals(compartment));
+      nsJSPrincipals::get(JS::GetRealmPrincipals(realm));
     aDocument->NodePrincipal()->Equals(existing, &sameOrigin);
     MOZ_ASSERT(sameOrigin);
-#endif
+
+    JSCompartment* compartment = JS::GetCompartmentForRealm(realm);
     MOZ_ASSERT_IF(aDocument == oldDoc,
                   xpc::GetCompartmentPrincipal(compartment) ==
                   aDocument->NodePrincipal());
+#endif
     if (aDocument != oldDoc) {
-      JS_SetCompartmentPrincipals(compartment,
-                                  nsJSPrincipals::get(aDocument->NodePrincipal()));
+      JS::SetRealmPrincipals(realm,
+                             nsJSPrincipals::get(aDocument->NodePrincipal()));
       // Make sure we clear out the old content XBL scope, so the new one will
       // get created with a principal that subsumes our new principal.
       xpc::ClearContentXBLScope(newInnerGlobal);
     }
   } else {
     if (aState) {
       newInnerWindow = wsh->GetInnerWindow();
       newInnerGlobal = newInnerWindow->GetWrapperPreserveColor();
@@ -1975,23 +1977,23 @@ nsGlobalWindowOuter::SetNewDocument(nsID
   // We no longer need the old inner window.  Start its destruction if
   // its not being reused and clear our reference.
   if (doomCurrentInner) {
     currentInner->FreeInnerObjects();
   }
   currentInner = nullptr;
 
   // Ask the JS engine to assert that it's valid to access our DocGroup whenever
-  // it runs JS code for this compartment. We skip the check if this window is
-  // for chrome JS or an add-on.
+  // it runs JS code for this realm. We skip the check if this window is for
+  // chrome JS or an add-on.
   nsCOMPtr<nsIPrincipal> principal = mDoc->NodePrincipal();
   if (GetDocGroup() && !nsContentUtils::IsSystemPrincipal(principal) &&
       !BasePrincipal::Cast(principal)->AddonPolicy()) {
-    js::SetCompartmentValidAccessPtr(cx, newInnerGlobal,
-                                     newInnerWindow->GetDocGroup()->GetValidAccessPtr());
+    js::SetRealmValidAccessPtr(cx, newInnerGlobal,
+                               newInnerWindow->GetDocGroup()->GetValidAccessPtr());
   }
 
   kungFuDeathGrip->DidInitializeContext();
 
   // We wait to fire the debugger hook until the window is all set up and hooked
   // up with the outer. See bug 969156.
   if (createdInnerWindow) {
     nsContentUtils::AddScriptRunner(

--- a/dom/base/nsJSEnvironment.cpp
+++ b/dom/base/nsJSEnvironment.cpp
@@ -2558,31 +2558,31 @@ static bool
 AsmJSCacheOpenEntryForRead(JS::Handle<JSObject*> aGlobal,
                            const char16_t* aBegin,
                            const char16_t* aLimit,
                            size_t* aSize,
                            const uint8_t** aMemory,
                            intptr_t *aHandle)
 {
   nsIPrincipal* principal =
-    nsJSPrincipals::get(JS_GetCompartmentPrincipals(js::GetObjectCompartment(aGlobal)));
+    nsJSPrincipals::get(JS::GetRealmPrincipals(js::GetNonCCWObjectRealm(aGlobal)));
   return asmjscache::OpenEntryForRead(principal, aBegin, aLimit, aSize, aMemory,
                                       aHandle);
 }
 
 static JS::AsmJSCacheResult
 AsmJSCacheOpenEntryForWrite(JS::Handle<JSObject*> aGlobal,
                             const char16_t* aBegin,
                             const char16_t* aEnd,
                             size_t aSize,
                             uint8_t** aMemory,
                             intptr_t* aHandle)
 {
   nsIPrincipal* principal =
-    nsJSPrincipals::get(JS_GetCompartmentPrincipals(js::GetObjectCompartment(aGlobal)));
+    nsJSPrincipals::get(JS::GetRealmPrincipals(js::GetNonCCWObjectRealm(aGlobal)));
   return asmjscache::OpenEntryForWrite(principal, aBegin, aEnd, aSize, aMemory,
                                        aHandle);
 }
 
 class JSDispatchableRunnable final : public Runnable
 {
   ~JSDispatchableRunnable()
   {

--- a/dom/bindings/BindingUtils.cpp
+++ b/dom/bindings/BindingUtils.cpp
@@ -2457,19 +2457,19 @@ GlobalObject::GetAsSupports() const
 
 nsIPrincipal*
 GlobalObject::GetSubjectPrincipal() const
 {
   if (!NS_IsMainThread()) {
     return nullptr;
   }
 
-  JSCompartment* compartment = js::GetContextCompartment(mCx);
-  MOZ_ASSERT(compartment);
-  JSPrincipals* principals = JS_GetCompartmentPrincipals(compartment);
+  JS::Realm* realm = js::GetContextRealm(mCx);
+  MOZ_ASSERT(realm);
+  JSPrincipals* principals = JS::GetRealmPrincipals(realm);
   return nsJSPrincipals::get(principals);
 }
 
 CallerType
 GlobalObject::CallerType() const
 {
   return nsContentUtils::ThreadsafeIsSystemCaller(mCx) ?
     dom::CallerType::System : dom::CallerType::NonSystem;

--- a/dom/bindings/CallbackObject.cpp
+++ b/dom/bindings/CallbackObject.cpp
@@ -128,20 +128,20 @@ CallbackObject::Callback(JSContext* aCx)
   MOZ_DIAGNOSTIC_ASSERT(callback);
   return callback;
 }
 
 CallbackObject::CallSetup::CallSetup(CallbackObject* aCallback,
                                      ErrorResult& aRv,
                                      const char* aExecutionReason,
                                      ExceptionHandling aExceptionHandling,
-                                     JSCompartment* aCompartment,
+                                     JS::Realm* aRealm,
                                      bool aIsJSImplementedWebIDL)
   : mCx(nullptr)
-  , mCompartment(aCompartment)
+  , mRealm(aRealm)
   , mErrorResult(aRv)
   , mExceptionHandling(aExceptionHandling)
   , mIsMainThread(NS_IsMainThread())
 {
   CycleCollectedJSContext* ccjs = CycleCollectedJSContext::Get();
   if (ccjs) {
     ccjs->EnterMicroTask();
   }
@@ -256,69 +256,69 @@ CallbackObject::CallSetup::CallSetup(Cal
   // And now we're ready to go.
   mCx = cx;
 }
 
 bool
 CallbackObject::CallSetup::ShouldRethrowException(JS::Handle<JS::Value> aException)
 {
   if (mExceptionHandling == eRethrowExceptions) {
-    if (!mCompartment) {
+    if (!mRealm) {
       // Caller didn't ask us to filter for only exceptions we subsume.
       return true;
     }
 
     // On workers, we don't have nsIPrincipals to work with.  But we also only
-    // have one compartment, so check whether mCompartment is the same as the
-    // current compartment of mCx.
-    if (mCompartment == js::GetContextCompartment(mCx)) {
+    // have one realm, so check whether mRealm is the same as the current realm
+    // of mCx.
+    if (mRealm == js::GetContextRealm(mCx)) {
       return true;
     }
 
     MOZ_ASSERT(NS_IsMainThread());
 
-    // At this point mCx is in the compartment of our unwrapped callback, so
-    // just check whether the principal of mCompartment subsumes that of the
-    // current compartment/global of mCx.
+    // At this point mCx is in the realm of our unwrapped callback, so just
+    // check whether the principal of mRealm subsumes that of the current
+    // realm/global of mCx.
     nsIPrincipal* callerPrincipal =
-      nsJSPrincipals::get(JS_GetCompartmentPrincipals(mCompartment));
+      nsJSPrincipals::get(JS::GetRealmPrincipals(mRealm));
     nsIPrincipal* calleePrincipal = nsContentUtils::SubjectPrincipal();
     if (callerPrincipal->SubsumesConsideringDomain(calleePrincipal)) {
       return true;
     }
   }
 
-  MOZ_ASSERT(mCompartment);
+  MOZ_ASSERT(mRealm);
 
   // Now we only want to throw an exception to the caller if the object that was
-  // thrown is in the caller compartment (which we stored in mCompartment).
+  // thrown is in the caller realm (which we stored in mRealm).
 
   if (!aException.isObject()) {
     return false;
   }
 
   JS::Rooted<JSObject*> obj(mCx, &aException.toObject());
   obj = js::UncheckedUnwrap(obj, /* stopAtWindowProxy = */ false);
-  return js::GetObjectCompartment(obj) == mCompartment;
+  return js::GetNonCCWObjectRealm(obj) == mRealm;
 }
 
 CallbackObject::CallSetup::~CallSetup()
 {
   // To get our nesting right we have to destroy our JSAutoRealm first.
   // In particular, we want to do this before we try reporting any exceptions,
   // so we end up reporting them while in the realm of our entry point,
   // not whatever cross-compartment wrappper mCallback might be.
   // Be careful: the JSAutoRealm might not have been constructed at all!
   mAr.reset();
 
   // Now, if we have a JSContext, report any pending errors on it, unless we
   // were told to re-throw them.
   if (mCx) {
     bool needToDealWithException = mAutoEntryScript->HasException();
-    if ((mCompartment && mExceptionHandling == eRethrowContentExceptions) ||
+    if ((mRealm && mExceptionHandling == eRethrowContentExceptions) ||
         mExceptionHandling == eRethrowExceptions) {
       mErrorResult.MightThrowJSException();
       if (needToDealWithException) {
         JS::Rooted<JS::Value> exn(mCx);
         if (mAutoEntryScript->PeekException(&exn) &&
             ShouldRethrowException(exn)) {
           mAutoEntryScript->ClearException();
           MOZ_ASSERT(!mAutoEntryScript->HasException());
@@ -344,17 +344,17 @@ CallbackObject::CallSetup::~CallSetup()
       }
     }
   }
 
   mAutoIncumbentScript.reset();
   mAutoEntryScript.reset();
 
   // It is important that this is the last thing we do, after leaving the
-  // compartment and undoing all our entry/incumbent script changes
+  // realm and undoing all our entry/incumbent script changes
   CycleCollectedJSContext* ccjs = CycleCollectedJSContext::Get();
   if (ccjs) {
     ccjs->LeaveMicroTask();
   }
 }
 
 already_AddRefed<nsISupports>
 CallbackObjectHolderBase::ToXPCOMCallback(CallbackObject* aCallback,

--- a/dom/bindings/CallbackObject.h
+++ b/dom/bindings/CallbackObject.h
@@ -89,17 +89,17 @@ public:
   // doesn't trigger any scripts before it accesses it.
   JS::Handle<JSObject*> CallbackOrNull() const
   {
     mCallback.exposeToActiveJS();
     return CallbackPreserveColor();
   }
 
   // Like CallbackOrNull(), but will return a new dead proxy object in the
-  // caller's compartment if the callback is null.
+  // caller's realm if the callback is null.
   JSObject* Callback(JSContext* aCx);
 
   JSObject* GetCreationStack() const
   {
     return mCreationStack;
   }
 
   void MarkForCC()
@@ -141,20 +141,19 @@ public:
 
   enum ExceptionHandling {
     // Report any exception and don't throw it to the caller code.
     eReportExceptions,
     // Throw an exception to the caller code if the thrown exception is a
     // binding object for a DOMException from the caller's scope, otherwise
     // report it.
     eRethrowContentExceptions,
-    // Throw exceptions to the caller code, unless the caller compartment is
+    // Throw exceptions to the caller code, unless the caller realm is
     // provided, the exception is not a DOMException from the caller
-    // compartment, and the caller compartment does not subsume our unwrapped
-    // callback.
+    // realm, and the caller realm does not subsume our unwrapped callback.
     eRethrowExceptions
   };
 
   size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const
   {
     return aMallocSizeOf(this);
   }
 
@@ -290,27 +289,27 @@ protected:
   {
     /**
      * A class that performs whatever setup we need to safely make a
      * call while this class is on the stack, After the constructor
      * returns, the call is safe to make if GetContext() returns
      * non-null.
      */
   public:
-    // If aExceptionHandling == eRethrowContentExceptions then aCompartment
-    // needs to be set to the compartment in which exceptions will be rethrown.
+    // If aExceptionHandling == eRethrowContentExceptions then aRealm
+    // needs to be set to the realm in which exceptions will be rethrown.
     //
-    // If aExceptionHandling == eRethrowExceptions then aCompartment may be set
-    // to the compartment in which exceptions will be rethrown.  In that case
-    // they will only be rethrown if that compartment's principal subsumes the
+    // If aExceptionHandling == eRethrowExceptions then aRealm may be set
+    // to the realm in which exceptions will be rethrown.  In that case
+    // they will only be rethrown if that realm's principal subsumes the
     // principal of our (unwrapped) callback.
     CallSetup(CallbackObject* aCallback, ErrorResult& aRv,
               const char* aExecutionReason,
               ExceptionHandling aExceptionHandling,
-              JSCompartment* aCompartment = nullptr,
+              JS::Realm* aRealm = nullptr,
               bool aIsJSImplementedWebIDL = false);
     ~CallSetup();
 
     JSContext* GetContext() const
     {
       return mCx;
     }
 
@@ -318,19 +317,19 @@ protected:
     // We better not get copy-constructed
     CallSetup(const CallSetup&) = delete;
 
     bool ShouldRethrowException(JS::Handle<JS::Value> aException);
 
     // Members which can go away whenever
     JSContext* mCx;
 
-    // Caller's compartment. This will only have a sensible value if
+    // Caller's realm. This will only have a sensible value if
     // mExceptionHandling == eRethrowContentExceptions or eRethrowExceptions.
-    JSCompartment* mCompartment;
+    JS::Realm* mRealm;
 
     // And now members whose construction/destruction order we need to control.
     Maybe<AutoEntryScript> mAutoEntryScript;
     Maybe<AutoIncumbentScript> mAutoIncumbentScript;
 
     Maybe<JS::Rooted<JSObject*> > mRootedCallable;
 
     // Members which are used to set the async stack.

--- a/dom/bindings/Codegen.py
+++ b/dom/bindings/Codegen.py
@@ -7231,19 +7231,19 @@ class CGCallGenerator(CGThing):
                       principal = nullptr;
                     }
                     """)
             else:
                 checkPrincipal = ""
 
             getPrincipal = fill(
                 """
-                JSCompartment* compartment = js::GetContextCompartment(cx);
-                MOZ_ASSERT(compartment);
-                JSPrincipals* principals = JS_GetCompartmentPrincipals(compartment);
+                JS::Realm* realm = js::GetContextRealm(cx);
+                MOZ_ASSERT(realm);
+                JSPrincipals* principals = JS::GetRealmPrincipals(realm);
                 nsIPrincipal* principal = nsJSPrincipals::get(principals);
                 ${checkPrincipal}
                 """,
                 checkPrincipal=checkPrincipal)
 
             if descriptor.interface.isExposedInAnyWorker():
                 self.cgRoot.prepend(CGGeneric(fill(
                     """
@@ -7558,17 +7558,17 @@ class CGPerSignatureCall(CGThing):
             if descriptor.interface.isJSImplemented():
                 # We need the desired proto in our constructor, because the
                 # constructor will actually construct our reflector.
                 argsPost.append("desiredProto")
         elif descriptor.interface.isJSImplemented():
             if not idlNode.isStatic():
                 needsUnwrap = True
                 needsUnwrappedVar = True
-                argsPost.append("js::GetObjectCompartment(unwrappedObj ? *unwrappedObj : obj)")
+                argsPost.append("(unwrappedObj ? js::GetNonCCWObjectRealm(*unwrappedObj) : js::GetContextRealm(cx))")
         elif needScopeObject(returnType, arguments, self.extendedAttributes,
                              descriptor.wrapperCache, True,
                              idlNode.getExtendedAttribute("StoreInSlot")):
             needsUnwrap = True
             needsUnwrappedVar = True
             argsPre.append("unwrappedObj ? *unwrappedObj : obj")
 
         if needsUnwrap and needsUnwrappedVar:
@@ -15004,17 +15004,17 @@ class CGJSImplMember(CGNativeMember):
                                 visibility=visibility,
                                 variadicIsSequence=variadicIsSequence,
                                 virtual=virtual,
                                 override=override)
         self.body = self.getImpl()
 
     def getArgs(self, returnType, argList):
         args = CGNativeMember.getArgs(self, returnType, argList)
-        args.append(Argument("JSCompartment*", "aCompartment", "nullptr"))
+        args.append(Argument("JS::Realm*", "aRealm", "nullptr"))
         return args
 
 
 class CGJSImplMethod(CGJSImplMember):
     """
     Class for generating code for the methods for a JS-implemented WebIDL
     interface.
     """
@@ -15053,17 +15053,17 @@ class CGJSImplMethod(CGJSImplMember):
             # arguments to the WebIDL constructor, so don't pass them to
             # __Init().  The last argument is the prototype we're supposed to
             # use, and shouldn't get passed to __Init() either.
             assert args[0].argType == 'const GlobalObject&'
             assert args[1].argType == 'JSContext*'
             assert args[-1].argType == 'JS::Handle<JSObject*>'
             assert args[-1].name == 'aGivenProto'
             constructorArgs = [arg.name for arg in args[2:-1]]
-            constructorArgs.append("js::GetObjectCompartment(scopeObj)")
+            constructorArgs.append("js::GetNonCCWObjectRealm(scopeObj)")
             initCall = fill(
                 """
                 // Wrap the object before calling __Init so that __DOM_IMPL__ is available.
                 JS::Rooted<JSObject*> scopeObj(cx, globalHolder->GetGlobalJSObject());
                 MOZ_ASSERT(js::IsObjectInContextCompartment(scopeObj, cx));
                 JS::Rooted<JS::Value> wrappedVal(cx);
                 if (!GetOrCreateDOMReflector(cx, impl, &wrappedVal, aGivenProto)) {
                   MOZ_ASSERT(JS_IsExceptionPending(cx));
@@ -15501,61 +15501,61 @@ class CGCallback(CGClass):
         argnamesWithThis = ["s.GetContext()", "thisValJS"] + argnames
         argnamesWithoutThis = ["s.GetContext()", "JS::UndefinedHandleValue"] + argnames
         # Now that we've recorded the argnames for our call to our private
         # method, insert our optional argument for the execution reason.
         args.append(Argument("const char*", "aExecutionReason",
                              "nullptr"))
 
         # Make copies of the arg list for the two "without rv" overloads.  Note
-        # that those don't need aExceptionHandling or aCompartment arguments
-        # because those would make not sense anyway: the only sane thing to do
-        # with exceptions in the "without rv" cases is to report them.
+        # that those don't need aExceptionHandling or aRealm arguments because
+        # those would make not sense anyway: the only sane thing to do with
+        # exceptions in the "without rv" cases is to report them.
         argsWithoutRv = list(args)
         argsWithoutRv.pop(rvIndex)
         argsWithoutThisAndRv = list(argsWithoutRv)
 
         # Add the potional argument for deciding whether the CallSetup should
         # re-throw exceptions on aRv.
         args.append(Argument("ExceptionHandling", "aExceptionHandling",
                              "eReportExceptions"))
         # And the argument for communicating when exceptions should really be
         # rethrown.  In particular, even when aExceptionHandling is
-        # eRethrowExceptions they won't get rethrown if aCompartment is provided
+        # eRethrowExceptions they won't get rethrown if aRealm is provided
         # and its principal doesn't subsume either the callback or the
         # exception.
-        args.append(Argument("JSCompartment*", "aCompartment", "nullptr"))
+        args.append(Argument("JS::Realm*", "aRealm", "nullptr"))
         # And now insert our template argument.
         argsWithoutThis = list(args)
         args.insert(0, Argument("const T&",  "thisVal"))
         argsWithoutRv.insert(0, Argument("const T&",  "thisVal"))
 
         argnamesWithoutThisAndRv = [arg.name for arg in argsWithoutThisAndRv]
         argnamesWithoutThisAndRv.insert(rvIndex, "IgnoreErrors()");
         # If we just leave things like that, and have no actual arguments in the
         # IDL, we will end up trying to call the templated "without rv" overload
         # with "rv" as the thisVal.  That's no good.  So explicitly append the
-        # aExceptionHandling and aCompartment values we need to end up matching
-        # the signature of our non-templated "with rv" overload.
+        # aExceptionHandling and aRealm values we need to end up matching the
+        # signature of our non-templated "with rv" overload.
         argnamesWithoutThisAndRv.extend(["eReportExceptions", "nullptr"])
 
         argnamesWithoutRv = [arg.name for arg in argsWithoutRv]
         # Note that we need to insert at rvIndex + 1, since we inserted a
         # thisVal arg at the start.
         argnamesWithoutRv.insert(rvIndex + 1, "IgnoreErrors()")
 
         errorReturn = method.getDefaultRetval()
 
         setupCall = fill(
             """
             MOZ_ASSERT(!aRv.Failed(), "Don't pass an already-failed ErrorResult to a callback!");
             if (!aExecutionReason) {
               aExecutionReason = "${executionReason}";
             }
-            CallSetup s(this, aRv, aExecutionReason, aExceptionHandling, aCompartment);
+            CallSetup s(this, aRv, aExecutionReason, aExceptionHandling, aRealm);
             if (!s.GetContext()) {
               MOZ_ASSERT(aRv.Failed());
               return${errorReturn};
             }
             """,
             errorReturn=errorReturn,
             executionReason=method.getPrettyName())
 
@@ -15956,35 +15956,35 @@ class CallbackMember(CGNativeMember):
         if not self.needThisHandling:
             # Since we don't need this handling, we're the actual method that
             # will be called, so we need an aRethrowExceptions argument.
             if not self.rethrowContentException:
                 args.append(Argument("const char*", "aExecutionReason",
                                      "nullptr"))
                 args.append(Argument("ExceptionHandling", "aExceptionHandling",
                                      "eReportExceptions"))
-            args.append(Argument("JSCompartment*", "aCompartment", "nullptr"))
+            args.append(Argument("JS::Realm*", "aRealm", "nullptr"))
             return args
         # We want to allow the caller to pass in a "this" value, as
         # well as a JSContext.
         return [Argument("JSContext*", "cx"),
                 Argument("JS::Handle<JS::Value>", "aThisVal")] + args
 
     def getCallSetup(self):
         if self.needThisHandling:
             # It's been done for us already
             return ""
         callSetup = "CallSetup s(this, aRv"
         if self.rethrowContentException:
             # getArgs doesn't add the aExceptionHandling argument but does add
-            # aCompartment for us.
-            callSetup += ', "%s", eRethrowContentExceptions, aCompartment, /* aIsJSImplementedWebIDL = */ ' % self.getPrettyName()
+            # aRealm for us.
+            callSetup += ', "%s", eRethrowContentExceptions, aRealm, /* aIsJSImplementedWebIDL = */ ' % self.getPrettyName()
             callSetup += toStringBool(isJSImplementedDescriptor(self.descriptorProvider))
         else:
-            callSetup += ', "%s", aExceptionHandling, aCompartment' % self.getPrettyName()
+            callSetup += ', "%s", aExceptionHandling, aRealm' % self.getPrettyName()
         callSetup += ");\n"
         return fill(
             """
             $*{callSetup}
             JSContext* cx = s.GetContext();
             if (!cx) {
               MOZ_ASSERT(aRv.Failed());
               return${errorReturn};

--- a/dom/bindings/Exceptions.cpp
+++ b/dom/bindings/Exceptions.cpp
@@ -184,17 +184,17 @@ CreateException(nsresult aRv, const nsAC
 }
 
 already_AddRefed<nsIStackFrame>
 GetCurrentJSStack(int32_t aMaxDepth)
 {
   // is there a current context available?
   JSContext* cx = nsContentUtils::GetCurrentJSContext();
 
-  if (!cx || !js::GetContextCompartment(cx)) {
+  if (!cx || !js::GetContextRealm(cx)) {
     return nullptr;
   }
 
   static const unsigned MAX_FRAMES = 100;
   if (aMaxDepth < 0) {
     aMaxDepth = MAX_FRAMES;
   }
 

--- a/dom/bindings/test/mochitest.ini
+++ b/dom/bindings/test/mochitest.ini
@@ -68,16 +68,18 @@ skip-if = debug == false
 [test_unforgeablesonexpando.html]
 [test_crossOriginWindowSymbolAccess.html]
 [test_primitive_this.html]
 [test_callback_exceptions.html]
 [test_bug1123516_maplikesetlike.html]
 skip-if = debug == false
 [test_jsimplemented_eventhandler.html]
 skip-if = debug == false
+[test_jsimplemented_cross_realm_this.html]
+skip-if = debug == false
 [test_iterable.html]
 skip-if = debug == false
 [test_oom_reporting.html]
 [test_domProxyArrayLengthGetter.html]
 [test_exceptionSanitization.html]
 skip-if = debug == false
 [test_stringBindings.html]
 skip-if = debug == false

new file mode 100644
--- /dev/null
+++ b/dom/bindings/test/test_jsimplemented_cross_realm_this.html
@@ -0,0 +1,43 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=1464374-->
+<head>
+  <meta charset="utf-8">
+  <title>Test for Bug 1464374</title>
+  <script type="application/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1464374">Mozilla Bug 1464374</a>
+<p id="display"></p>
+<div id="content" style="display: none">
+
+</div>
+<pre id="test">
+</pre>
+
+<iframe></iframe>
+<script type="application/javascript">
+  /** Test for Bug 1464374 **/
+  SimpleTest.waitForExplicitFinish();
+
+  function doTest() {
+    var frame = frames[0];
+    var obj = new frame.TestInterfaceJS();
+    var ex;
+    try {
+      TestInterfaceJS.prototype.testThrowTypeError.call(obj);
+    } catch(e) {
+      ex = e;
+    }
+    ok(ex, "Should have an exception");
+    SimpleTest.finish();
+  }
+
+  SpecialPowers.pushPrefEnv({set: [['dom.expose_test_interfaces', true]]},
+                            doTest);
+</script>
+
+</body>
+</html>

--- a/dom/html/nsHTMLDocument.cpp
+++ b/dom/html/nsHTMLDocument.cpp
@@ -1532,20 +1532,20 @@ nsHTMLDocument::Open(JSContext* cx,
 
   CreateAndAddWyciwygChannel();
 
   --mWriteLevel;
 
   SetReadyStateInternal(nsIDocument::READYSTATE_LOADING);
 
   // After changing everything around, make sure that the principal on the
-  // document's compartment exactly matches NodePrincipal().
+  // document's realm exactly matches NodePrincipal().
   DebugOnly<JSObject*> wrapper = GetWrapperPreserveColor();
   MOZ_ASSERT_IF(wrapper,
-                JS_GetCompartmentPrincipals(js::GetObjectCompartment(wrapper)) ==
+                JS::GetRealmPrincipals(js::GetNonCCWObjectRealm(wrapper)) ==
                 nsJSPrincipals::get(NodePrincipal()));
 
   return kungFuDeathGrip.forget();
 }
 
 void
 nsHTMLDocument::Close(ErrorResult& rv)
 {

--- a/dom/script/ScriptSettings.cpp
+++ b/dom/script/ScriptSettings.cpp
@@ -613,17 +613,17 @@ AutoJSAPI::ReportException()
   }
 }
 
 bool
 AutoJSAPI::PeekException(JS::MutableHandle<JS::Value> aVal)
 {
   MOZ_ASSERT_IF(mIsMainThread, IsStackTop());
   MOZ_ASSERT(HasException());
-  MOZ_ASSERT(js::GetContextCompartment(cx()));
+  MOZ_ASSERT(js::GetContextRealm(cx()));
   if (!JS_GetPendingException(cx(), aVal)) {
     return false;
   }
   return true;
 }
 
 bool
 AutoJSAPI::StealException(JS::MutableHandle<JS::Value> aVal)

--- a/dom/security/nsContentSecurityManager.cpp
+++ b/dom/security/nsContentSecurityManager.cpp
@@ -885,22 +885,26 @@ nsContentSecurityManager::IsOriginPotent
   NS_WARNING_ASSERTION(!scheme.EqualsLiteral("blob"),
                        "IsOriginPotentiallyTrustworthy ignoring blob scheme");
 
   // According to the specification, the user agent may choose to extend the
   // trust to other, vendor-specific URL schemes. We use this for "resource:",
   // which is technically a substituting protocol handler that is not limited to
   // local resource mapping, but in practice is never mapped remotely as this
   // would violate assumptions a lot of code makes.
-  if (scheme.EqualsLiteral("https") ||
-      scheme.EqualsLiteral("file") ||
-      scheme.EqualsLiteral("resource") ||
-      scheme.EqualsLiteral("app") ||
-      scheme.EqualsLiteral("moz-extension") ||
-      scheme.EqualsLiteral("wss")) {
+  // We use nsIProtocolHandler flags to determine which protocols we consider a priori
+  // authenticated.
+  bool aPrioriAuthenticated = false;
+  if (NS_FAILED(NS_URIChainHasFlags(uri,
+                                    nsIProtocolHandler::URI_IS_POTENTIALLY_TRUSTWORTHY,
+                                    &aPrioriAuthenticated))) {
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  if (aPrioriAuthenticated) {
     *aIsTrustWorthy = true;
     return NS_OK;
   }
 
   nsAutoCString host;
   rv = uri->GetHost(host);
   if (NS_FAILED(rv)) {
     return NS_OK;

--- a/dom/security/nsMixedContentBlocker.cpp
+++ b/dom/security/nsMixedContentBlocker.cpp
@@ -592,29 +592,29 @@ nsMixedContentBlocker::ShouldLoad(bool a
   * URI_DOES_NOT_RETURN_DATA - e.g.
   *   "mailto"
   * URI_IS_LOCAL_RESOURCE - e.g.
   *   "data",
   *   "resource",
   *   "moz-icon"
   * URI_INHERITS_SECURITY_CONTEXT - e.g.
   *   "javascript"
-  * URI_SAFE_TO_LOAD_IN_SECURE_CONTEXT - e.g.
+  * URI_IS_POTENTIALLY_TRUSTWORTHY - e.g.
   *   "https",
   *   "moz-safe-about"
   *
   */
   bool schemeLocal = false;
   bool schemeNoReturnData = false;
   bool schemeInherits = false;
   bool schemeSecure = false;
   if (NS_FAILED(NS_URIChainHasFlags(innerContentLocation, nsIProtocolHandler::URI_IS_LOCAL_RESOURCE , &schemeLocal))  ||
       NS_FAILED(NS_URIChainHasFlags(innerContentLocation, nsIProtocolHandler::URI_DOES_NOT_RETURN_DATA, &schemeNoReturnData)) ||
       NS_FAILED(NS_URIChainHasFlags(innerContentLocation, nsIProtocolHandler::URI_INHERITS_SECURITY_CONTEXT, &schemeInherits)) ||
-      NS_FAILED(NS_URIChainHasFlags(innerContentLocation, nsIProtocolHandler::URI_SAFE_TO_LOAD_IN_SECURE_CONTEXT, &schemeSecure))) {
+      NS_FAILED(NS_URIChainHasFlags(innerContentLocation, nsIProtocolHandler::URI_IS_POTENTIALLY_TRUSTWORTHY, &schemeSecure))) {
     *aDecision = REJECT_REQUEST;
     return NS_ERROR_FAILURE;
   }
   // TYPE_IMAGE redirects are cached based on the original URI, not the final
   // destination and hence cache hits for images may not have the correct
   // innerContentLocation.  Check if the cached hit went through an http redirect,
   // and if it did, we can't treat this as a secure subresource.
   if (!aHadInsecureImageRedirect &&

new file mode 100644
--- /dev/null
+++ b/dom/security/test/gtest/TestSecureContext.cpp
@@ -0,0 +1,94 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "gtest/gtest.h"
+
+#include <string.h>
+#include <stdlib.h>
+
+#include "nsContentSecurityManager.h"
+#include "nsContentUtils.h"
+#include "nsIPrincipal.h"
+#include "nsScriptSecurityManager.h"
+#include "NullPrincipal.h"
+
+static const uint32_t kURIMaxLength = 64;
+
+struct TestExpectations {
+  char uri[kURIMaxLength ];
+  bool expectedResult;
+};
+
+// ============================= TestDirectives ========================
+
+TEST(SecureContext, IsOriginPotentiallyTrustworthyWithCodeBasePrincipal)
+{
+  //boolean isOriginPotentiallyTrustworthy(in nsIPrincipal aPrincipal);
+
+  static const TestExpectations uris[] = {
+    { "http://example.com/", false },
+    { "https://example.com/", true },
+    { "ws://example.com/", false },
+    { "wss://example.com/", true },
+    { "file:///xyzzy", true },
+    { "ftp://example.com", false },
+    { "about:config", false },
+    { "http://localhost", true },
+    { "http://xyzzy.localhost", false },
+    { "http://127.0.0.1", true },
+    { "resource://xyzzy", true },
+    { "moz-extension://xyzzy", true },
+    { "data:data:text/plain;charset=utf-8;base64,eHl6enk=", false },
+    { "blob://unique-id", false },
+    { "mailto:foo@bar.com", false },
+    { "moz-icon://example.com", false },
+    { "javascript:42", false },
+  };
+
+  uint32_t numExpectations = sizeof(uris) / sizeof(TestExpectations);
+  nsCOMPtr<nsIContentSecurityManager> csManager = do_GetService(NS_CONTENTSECURITYMANAGER_CONTRACTID);
+  ASSERT_TRUE(!!csManager);
+
+  nsresult rv;
+  for (uint32_t i = 0; i < numExpectations; i++) {
+    nsCOMPtr<nsIPrincipal> prin;
+    nsAutoCString uri(uris[i].uri);
+    rv = nsScriptSecurityManager::GetScriptSecurityManager()->
+           CreateCodebasePrincipalFromOrigin(uri, getter_AddRefs(prin));
+    bool isPotentiallyTrustworthy = false;
+    rv = csManager->IsOriginPotentiallyTrustworthy(prin, &isPotentiallyTrustworthy);
+    ASSERT_EQ(NS_OK, rv);
+    ASSERT_EQ(isPotentiallyTrustworthy, uris[i].expectedResult);
+  }
+}
+
+TEST(SecureContext, IsOriginPotentiallyTrustworthyWithSystemPrincipal)
+{
+  RefPtr<nsScriptSecurityManager> ssManager = nsScriptSecurityManager::GetScriptSecurityManager();
+  ASSERT_TRUE(!!ssManager);
+  nsCOMPtr<nsIContentSecurityManager> csManager = do_GetService(NS_CONTENTSECURITYMANAGER_CONTRACTID);
+  ASSERT_TRUE(!!csManager);
+
+  nsCOMPtr<nsIPrincipal> sysPrin = nsContentUtils::GetSystemPrincipal();
+  bool isPotentiallyTrustworthy;
+  nsresult rv = csManager->IsOriginPotentiallyTrustworthy(sysPrin, &isPotentiallyTrustworthy);
+  ASSERT_EQ(rv, NS_OK);
+  ASSERT_TRUE(isPotentiallyTrustworthy);
+}
+
+TEST(SecureContext, IsOriginPotentiallyTrustworthyWithNullPrincipal)
+{
+  RefPtr<nsScriptSecurityManager> ssManager = nsScriptSecurityManager::GetScriptSecurityManager();
+  ASSERT_TRUE(!!ssManager);
+  nsCOMPtr<nsIContentSecurityManager> csManager = do_GetService(NS_CONTENTSECURITYMANAGER_CONTRACTID);
+  ASSERT_TRUE(!!csManager);
+
+  RefPtr<NullPrincipal> nullPrin = NullPrincipal::CreateWithoutOriginAttributes();
+  bool isPotentiallyTrustworthy;
+  nsresult rv = csManager->IsOriginPotentiallyTrustworthy(nullPrin, &isPotentiallyTrustworthy);
+  ASSERT_EQ(rv, NS_OK);
+  ASSERT_TRUE(!isPotentiallyTrustworthy);
+}

--- a/dom/security/test/gtest/moz.build
+++ b/dom/security/test/gtest/moz.build
@@ -1,11 +1,16 @@
 # -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
 # vim: set filetype=python:
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 UNIFIED_SOURCES += [
      'TestCSPParser.cpp',
+     'TestSecureContext.cpp',
 ]
 
 FINAL_LIBRARY = 'xul-gtest'
+
+LOCAL_INCLUDES += [
+    '/caps',
+]

--- a/dom/tests/mochitest/chrome/chrome.ini
+++ b/dom/tests/mochitest/chrome/chrome.ini
@@ -41,22 +41,20 @@ support-files =
 [test_DOM_element_instanceof.xul]
 [test_activation.xul]
 tags = fullscreen
 [test_bug799299.xul]
 [test_bug800817.xul]
 [test_bug830858.xul]
 [test_bug1224790-1.xul]
 tags = openwindow
-# synthesizeNativeOSXClick does not work on 10.6
-skip-if = os != 'mac' || os_version == '10.6'
+skip-if = os != 'mac'
 [test_bug1224790-2.xul]
 tags = openwindow
-# synthesizeNativeOSXClick does not work on 10.6
-skip-if = os != 'mac' || os_version == '10.6'
+skip-if = os != 'mac'
 [test_callback_wrapping.xul]
 [test_clonewrapper.xul]
 [test_cyclecollector.xul]
 [test_docshell_swap.xul]
 [test_focus.xul]
 skip-if = os == 'linux' && !debug # bug 1296622
 [test_focus_docnav.xul]
 [test_focus_switchbinding.xul]

--- a/dom/workers/WorkerPrivate.cpp
+++ b/dom/workers/WorkerPrivate.cpp
@@ -1201,25 +1201,22 @@ public:
                       override
   {
     MOZ_ASSERT(!aRealmStats->extra);
 
     // ReportJSRuntimeExplicitTreeStats expects that
     // aRealmStats->extra is a xpc::RealmStatsExtras pointer.
     xpc::RealmStatsExtras* extras = new xpc::RealmStatsExtras;
 
-    // This is the |jsPathPrefix|.  Each worker has exactly two realms:
-    // one for atoms, and one for everything else.
+    // This is the |jsPathPrefix|.  Each worker has exactly one realm.
     JSCompartment* compartment = JS::GetCompartmentForRealm(aRealm);
     extras->jsPathPrefix.Assign(mRtPath);
     extras->jsPathPrefix += nsPrintfCString("zone(0x%p)/",
                                             (void *)js::GetCompartmentZone(compartment));
-    extras->jsPathPrefix += js::IsAtomsRealm(aRealm)
-                            ? NS_LITERAL_CSTRING("realm(web-worker-atoms)/")
-                            : NS_LITERAL_CSTRING("realm(web-worker)/");
+    extras->jsPathPrefix += NS_LITERAL_CSTRING("realm(web-worker)/");
 
     // This should never be used when reporting with workers (hence the "?!").
     extras->domPathPrefix.AssignLiteral("explicit/workers/?!/");
 
     MOZ_ASSERT(StartsWithExplicit(extras->jsPathPrefix));
     MOZ_ASSERT(StartsWithExplicit(extras->domPathPrefix));
 
     extras->location = nullptr;

--- a/gfx/config/gfxVars.h
+++ b/gfx/config/gfxVars.h
@@ -34,19 +34,21 @@ class gfxVarReceiver;
   _(PDMWMFDisableD3D11Dlls,     nsCString,        nsCString())          \
   _(PDMWMFDisableD3D9Dlls,      nsCString,        nsCString())          \
   _(DXInterop2Blocked,          bool,             false)                \
   _(DXNV12Blocked,              bool,             false)                \
   _(UseWebRender,               bool,             false)                \
   _(UseWebRenderANGLE,          bool,             false)                \
   _(UseWebRenderDCompWin,       bool,             false)                \
   _(UseWebRenderProgramBinary,  bool,             false)                \
+  _(UseWebRenderProgramBinaryDisk, bool,          false)                \
   _(WebRenderDebugFlags,        int32_t,          0)                    \
   _(ScreenDepth,                int32_t,          0)                    \
   _(GREDirectory,               nsString,         nsString())           \
+  _(ProfDirectory,              nsString,         nsString())           \
   _(UseOMTP,                    bool,             false)                \
   _(AllowD3D11KeyedMutex,       bool,             false)                \
 
   /* Add new entries above this line. */
 
 // Some graphics settings are computed on the UI process and must be
 // communicated to content and GPU processes. gfxVars helps facilitate
 // this. Its function is similar to gfxPrefs, except rather than hold

--- a/gfx/layers/client/MultiTiledContentClient.cpp
+++ b/gfx/layers/client/MultiTiledContentClient.cpp
@@ -321,17 +321,16 @@ void ClientMultiTiledLayerBuffer::Update
 
       // Reset
       mPaintTiles.clear();
       mTilingOrigin = IntPoint(std::numeric_limits<int32_t>::max(),
                                std::numeric_limits<int32_t>::max());
     }
 
     bool edgePaddingEnabled = gfxPrefs::TileEdgePaddingEnabled();
-
     for (uint32_t i = 0; i < mRetainedTiles.Length(); ++i) {
       TileClient& tile = mRetainedTiles[i];
 
       // Only worry about padding when not doing low-res because it simplifies
       // the math and the artifacts won't be noticable
       // Edge padding prevents sampling artifacts when compositing.
       if (edgePaddingEnabled && mResolution == 1 &&
           tile.mFrontBuffer && tile.mFrontBuffer->IsLocked()) {
@@ -437,16 +436,18 @@ ClientMultiTiledLayerBuffer::ValidateTil
   // Add the region we copied from the front buffer into the painted region
   extraPainted.MoveBy(aTileOrigin);
   extraPainted.And(extraPainted, mNewValidRegion);
 
   if (!backBuffer) {
     return false;
   }
 
+  // Get the targets to draw into, and create a dual target
+  // if we are using component alpha
   RefPtr<DrawTarget> dt = backBuffer->BorrowDrawTarget();
   RefPtr<DrawTarget> dtOnWhite;
   if (backBufferOnWhite) {
     dtOnWhite = backBufferOnWhite->BorrowDrawTarget();
   }
 
   if (!dt || (backBufferOnWhite && !dtOnWhite)) {
     aTile.DiscardBuffers();
@@ -455,49 +456,59 @@ ClientMultiTiledLayerBuffer::ValidateTil
 
   RefPtr<DrawTarget> drawTarget;
   if (dtOnWhite) {
     drawTarget = Factory::CreateDualDrawTarget(dt, dtOnWhite);
   } else {
     drawTarget = dt;
   }
 
-  auto clear = CapturedTiledPaintState::Clear{
-    dt,
-    dtOnWhite,
-    tileDirtyRegion
-  };
+  // We need to clear the dirty region of the tile before painting
+  // if we are painting non-opaque content
+  Maybe<CapturedTiledPaintState::Clear> clear = Nothing();
+  if (mode != SurfaceMode::SURFACE_OPAQUE) {
+    clear = Some(CapturedTiledPaintState::Clear{
+      dt,
+      dtOnWhite,
+      tileDirtyRegion
+    });
+  }
 
+  // Queue or execute the paint operation
   gfx::Tile paintTile;
   paintTile.mTileOrigin = gfx::IntPoint(aTileOrigin.x, aTileOrigin.y);
 
   if (aFlags & TilePaintFlags::Async) {
     RefPtr<CapturedTiledPaintState> asyncPaint = new CapturedTiledPaintState();
 
     RefPtr<DrawTargetCapture> captureDT =
       Factory::CreateCaptureDrawTarget(drawTarget->GetBackendType(),
                                        drawTarget->GetSize(),
                                        drawTarget->GetFormat());
     paintTile.mDrawTarget = captureDT;
     asyncPaint->mTarget = drawTarget;
     asyncPaint->mCapture = captureDT;
 
     asyncPaint->mCopies = std::move(asyncPaintCopies);
-    asyncPaint->mClears.push_back(clear);
+    if (clear) {
+      asyncPaint->mClears.push_back(*clear);
+    }
 
     asyncPaint->mClients = std::move(asyncPaintClients);
     asyncPaint->mClients.push_back(backBuffer);
     if (backBufferOnWhite) {
       asyncPaint->mClients.push_back(backBufferOnWhite);
     }
 
     mPaintStates.push_back(asyncPaint);
   } else {
     paintTile.mDrawTarget = drawTarget;
-    clear.ClearBuffer();
+    if (clear) {
+      clear->ClearBuffer();
+    }
   }
 
   mPaintTiles.push_back(paintTile);
 
   mTilingOrigin.x = std::min(mTilingOrigin.x, paintTile.mTileOrigin.x);
   mTilingOrigin.y = std::min(mTilingOrigin.y, paintTile.mTileOrigin.y);
 
   // The new buffer is now validated, remove the dirty region from it.

--- a/gfx/layers/client/SingleTiledContentClient.cpp
+++ b/gfx/layers/client/SingleTiledContentClient.cpp
@@ -192,78 +192,31 @@ ClientSingleTiledLayerBuffer::PaintThebe
 
   // If the old frontbuffer was discarded then attempt to copy what we
   // can from it to the new backbuffer.
   if (discardedFrontBuffer) {
     nsIntRegion copyableRegion;
     copyableRegion.And(aNewValidRegion, discardedValidRegion);
     copyableRegion.SubOut(aDirtyRegion);
 
-    if (!copyableRegion.IsEmpty()) {
-      OpenMode asyncFlags = asyncPaint ? OpenMode::OPEN_ASYNC
-                                       : OpenMode::OPEN_NONE;
-
-      TextureClientAutoLock frontLock(discardedFrontBuffer,
-                                      OpenMode::OPEN_READ | asyncFlags);
-      Maybe<TextureClientAutoLock> frontOnWhiteLock;
-      if (discardedFrontBufferOnWhite && backBufferOnWhite) {
-        frontOnWhiteLock.emplace(discardedFrontBufferOnWhite, OpenMode::OPEN_READ | asyncFlags);
-      }
-
-      // Copy to both backBuffer and backBufferOnWhite if required, or copy to neither.
-      if (frontLock.Succeeded() && (!frontOnWhiteLock || frontOnWhiteLock->Succeeded())) {
-        RefPtr<gfx::DrawTarget> frontBuffer = discardedFrontBuffer->BorrowDrawTarget();
-
-        if (frontBuffer) {
-          for (auto iter = copyableRegion.RectIter(); !iter.Done(); iter.Next()) {
-            const gfx::IntRect rect = iter.Get() - discardedValidRegion.GetBounds().TopLeft();
-            const gfx::IntPoint dest = iter.Get().TopLeft() - mTilingOrigin;
-
-            auto copy = CapturedTiledPaintState::Copy{
-              frontBuffer, dt, rect, dest
-            };
-            if (asyncPaint) {
-              paintCopies.push_back(copy);
-            } else {
-              copy.CopyBuffer();
-            }
-          }
+    if (!mTile.CopyFromBuffer(discardedFrontBuffer,
+                              discardedFrontBufferOnWhite,
+                              discardedValidRegion.GetBounds().TopLeft(),
+                              mTilingOrigin,
+                              copyableRegion,
+                              aFlags,
+                              &paintCopies)) {
+      gfxWarning() << "[Tiling:Client] Failed to aquire the discarded front buffer's draw target";
+    } else {
+      TILING_LOG("TILING %p: Region copied from discarded frontbuffer %s\n", &mPaintedLayer, Stringify(copyableRegion).c_str());
 
-          if (frontOnWhiteLock) {
-            RefPtr<gfx::DrawTarget> frontBufferOnWhite = discardedFrontBufferOnWhite->BorrowDrawTarget();
-
-            if (frontBufferOnWhite) {
-              for (auto iter = copyableRegion.RectIter(); !iter.Done(); iter.Next()) {
-                const gfx::IntRect rect = iter.Get() - discardedValidRegion.GetBounds().TopLeft();
-                const gfx::IntPoint dest = iter.Get().TopLeft() - mTilingOrigin;
-
-                auto copy = CapturedTiledPaintState::Copy{
-                  frontBufferOnWhite, dtOnWhite, rect, dest
-                };
-                if (asyncPaint) {
-                  paintCopies.push_back(copy);
-                } else {
-                  copy.CopyBuffer();
-                }
-              }
-            } else {
-              gfxWarning() << "[Tiling:Client] Failed to aquire the discarded front buffer's draw target";
-            }
-          }
-        } else {
-          gfxWarning() << "[Tiling:Client] Failed to aquire the discarded front buffer's draw target";
-        }
-
-        TILING_LOG("TILING %p: Region copied from discarded frontbuffer %s\n", &mPaintedLayer, Stringify(copyableRegion).c_str());
-
-        // We don't need to repaint valid content that was just copied.
-        paintRegion.SubOut(copyableRegion);
-        copyableRegion.MoveBy(-mTilingOrigin);
-        tileDirtyRegion.SubOut(copyableRegion);
-      }
+      // We don't need to repaint valid content that was just copied.
+      paintRegion.SubOut(copyableRegion);
+      copyableRegion.MoveBy(-mTilingOrigin);
+      tileDirtyRegion.SubOut(copyableRegion);
     }
   }
 
   if (mode != SurfaceMode::SURFACE_OPAQUE) {
     auto clear = CapturedTiledPaintState::Clear{
       dt,
       dtOnWhite,
       tileDirtyRegion,

--- a/gfx/layers/client/TiledContentClient.cpp
+++ b/gfx/layers/client/TiledContentClient.cpp
@@ -478,55 +478,59 @@ CopyFrontToBack(TextureClient* aFront,
 void
 TileClient::ValidateBackBufferFromFront(const nsIntRegion& aDirtyRegion,
                                         const nsIntRegion& aVisibleRegion,
                                         nsIntRegion& aAddPaintedRegion,
                                         TilePaintFlags aFlags,
                                         std::vector<CapturedTiledPaintState::Copy>* aCopies,
                                         std::vector<RefPtr<TextureClient>>* aClients)
 {
-  if (mBackBuffer && mFrontBuffer) {
-    gfx::IntSize tileSize = mFrontBuffer->GetSize();
-    const IntRect tileRect = IntRect(0, 0, tileSize.width, tileSize.height);
+  if (!mBackBuffer || !mFrontBuffer) {
+    return;
+  }
+
+  gfx::IntSize tileSize = mFrontBuffer->GetSize();
+  const IntRect tileRect = IntRect(0, 0, tileSize.width, tileSize.height);
 
-    if (aDirtyRegion.Contains(tileRect)) {
-      // The dirty region means that we no longer need the front buffer, so
-      // discard it.
-      DiscardFrontBuffer();
-    } else {
-      // Region that needs copying.
-      nsIntRegion regionToCopy = mInvalidBack;
+  if (aDirtyRegion.Contains(tileRect)) {
+    // The dirty region means that we no longer need the front buffer, so
+    // discard it.
+    DiscardFrontBuffer();
+    return;
+  }
 
-      regionToCopy.Sub(regionToCopy, aDirtyRegion);
-      regionToCopy.And(regionToCopy, aVisibleRegion);
+  // Region that needs copying.
+  nsIntRegion regionToCopy = mInvalidBack;
 
-      aAddPaintedRegion = regionToCopy;
+  regionToCopy.Sub(regionToCopy, aDirtyRegion);
+  regionToCopy.And(regionToCopy, aVisibleRegion);
 
-      if (regionToCopy.IsEmpty()) {
-        // Just redraw it all.
-        return;
-      }
+  aAddPaintedRegion = regionToCopy;
+
+  if (regionToCopy.IsEmpty()) {
+    // Just redraw it all.
+    return;
+  }
 
-      // Copy the bounding rect of regionToCopy. As tiles are quite small, it
-      // is unlikely that we'd save much by copying each individual rect of the
-      // region, but we can reevaluate this if it becomes an issue.
-      const IntRect rectToCopy = regionToCopy.GetBounds();
-      gfx::IntRect gfxRectToCopy(rectToCopy.X(), rectToCopy.Y(), rectToCopy.Width(), rectToCopy.Height());
-      if (CopyFrontToBack(mFrontBuffer, mBackBuffer, gfxRectToCopy, aFlags, aCopies, aClients)) {
-        if (mBackBufferOnWhite) {
-          MOZ_ASSERT(mFrontBufferOnWhite);
-          if (CopyFrontToBack(mFrontBufferOnWhite, mBackBufferOnWhite, gfxRectToCopy, aFlags, aCopies, aClients)) {
-            mInvalidBack.Sub(mInvalidBack, aVisibleRegion);
-          }
-        } else {
-          mInvalidBack.Sub(mInvalidBack, aVisibleRegion);
-        }
-      }
+  // Copy the bounding rect of regionToCopy. As tiles are quite small, it
+  // is unlikely that we'd save much by copying each individual rect of the
+  // region, but we can reevaluate this if it becomes an issue.
+  const IntRect rectToCopy = regionToCopy.GetBounds();
+  if (!CopyFrontToBack(mFrontBuffer, mBackBuffer, rectToCopy, aFlags, aCopies, aClients)) {
+    return;
+  }
+
+  if (mBackBufferOnWhite) {
+    MOZ_ASSERT(mFrontBufferOnWhite);
+    if (!CopyFrontToBack(mFrontBufferOnWhite, mBackBufferOnWhite, rectToCopy, aFlags, aCopies, aClients)) {
+      return;
     }
   }
+
+  mInvalidBack.Sub(mInvalidBack, aVisibleRegion);
 }
 
 void
 TileClient::DiscardFrontBuffer()
 {
   if (mFrontBuffer) {
     MOZ_ASSERT(mFrontBuffer->GetReadLock());
 
@@ -575,16 +579,69 @@ TileClient::DiscardBackBuffer()
   if (mBackBuffer) {
     DiscardTexture(mBackBuffer, mAllocator);
     mBackBuffer.Set(this, nullptr);
     DiscardTexture(mBackBufferOnWhite, mAllocator);
     mBackBufferOnWhite = nullptr;
   }
 }
 
+bool
+TileClient::CopyFromBuffer(RefPtr<TextureClient> aBuffer,
+                           RefPtr<TextureClient> aBufferOnWhite,
+                           nsIntPoint aBufferOrigin,
+                           nsIntPoint aTileOrigin,
+                           const nsIntRegion& aRegion,
+                           TilePaintFlags aFlags,
+                           std::vector<CapturedTiledPaintState::Copy>* aCopies)
+{
+  if (aRegion.IsEmpty()) {
+    return true;
+  }
+
+  bool asyncPaint = !!(aFlags & TilePaintFlags::Async);
+  auto CopyBuffer = [&aRegion, asyncPaint, &aCopies] (auto aSrc, auto aSrcOrigin, auto aDest, auto aDestOrigin) {
+    MOZ_ASSERT(aDest->IsLocked());
+
+    OpenMode asyncFlags = asyncPaint ? OpenMode::OPEN_ASYNC
+                                     : OpenMode::OPEN_NONE;
+    TextureClientAutoLock lock(aSrc, OpenMode::OPEN_READ | asyncFlags);
+    if (!lock.Succeeded()) {
+      return false;
+    }
+
+    RefPtr<gfx::DrawTarget> srcTarget = aSrc->BorrowDrawTarget();
+    RefPtr<gfx::DrawTarget> destTarget = aDest->BorrowDrawTarget();
+    if (!srcTarget || !destTarget) {
+      return false;
+    }
+
+    for (auto iter = aRegion.RectIter(); !iter.Done(); iter.Next()) {
+      const gfx::IntRect src = iter.Get() - aSrcOrigin;
+      const gfx::IntPoint dest = iter.Get().TopLeft() - aDestOrigin;
+
+      auto copy = CapturedTiledPaintState::Copy{
+        srcTarget, destTarget, src, dest
+      };
+
+      if (asyncPaint) {
+        aCopies->push_back(copy);
+      } else {
+        copy.CopyBuffer();
+      }
+    }
+    return true;
+  };
+
+  return CopyBuffer(aBuffer, aBufferOrigin, mBackBuffer, aTileOrigin) &&
+    (!aBufferOnWhite ||
+     !mBackBufferOnWhite ||
+     CopyBuffer(aBufferOnWhite, aBufferOrigin, mBackBufferOnWhite, aTileOrigin));
+}
+
 static already_AddRefed<TextureClient>
 CreateBackBufferTexture(TextureClient* aCurrentTexture,
                         CompositableClient& aCompositable,
                         TextureClientAllocator* aAllocator)
 {
   if (aCurrentTexture) {
     // Our current back-buffer is still locked by the compositor. This can occur
     // when the client is producing faster than the compositor can consume. In

--- a/gfx/layers/client/TiledContentClient.h
+++ b/gfx/layers/client/TiledContentClient.h
@@ -135,16 +135,28 @@ struct TileClient
                                RefPtr<TextureClient>* aTextureClientOnWhite,
                                std::vector<CapturedTiledPaintState::Copy>* aCopies,
                                std::vector<RefPtr<TextureClient>>* aClients);
 
   void DiscardFrontBuffer();
 
   void DiscardBackBuffer();
 
+  /*
+   * Copy aRegion from aBuffer and aBufferOnWhite positioned at aBufferOrigin
+   * into ourselves assuming we are positioned at aTileOrigin.
+   */
+  bool CopyFromBuffer(RefPtr<TextureClient> aBuffer,
+                      RefPtr<TextureClient> aBufferOnWhite,
+                      nsIntPoint aBufferOrigin,
+                      nsIntPoint aTileOrigin,
+                      const nsIntRegion& aRegion,
+                      TilePaintFlags aFlags,
+                      std::vector<CapturedTiledPaintState::Copy>* aCopies);
+
   /* We wrap the back buffer in a class that disallows assignment
    * so that we can track when ever it changes so that we can update
    * the expiry tracker for expiring the back buffers */
   class PrivateProtector {
     public:
       void Set(TileClient * container, RefPtr<TextureClient>);
       void Set(TileClient * container, TextureClient*);
       // Implicitly convert to TextureClient* because we can't chain
@@ -163,18 +175,20 @@ struct TileClient
   bool mWasPlaceholder;
 #ifdef GFX_TILEDLAYER_DEBUG_OVERLAY
   TimeStamp        mLastUpdate;
 #endif
   nsIntRegion mInvalidFront;
   nsIntRegion mInvalidBack;
   nsExpirationState mExpirationState;
 private:
-  // Copies dirty pixels from the front buffer into the back buffer,
-  // and records the copied region in aAddPaintedRegion.
+  /*
+   * Copies dirty pixels from the front buffer into the back buffer,
+   * and records the copied region in aAddPaintedRegion.
+   */
   void ValidateBackBufferFromFront(const nsIntRegion &aDirtyRegion,
                                    const nsIntRegion& aVisibleRegion,
                                    nsIntRegion& aAddPaintedRegion,
                                    TilePaintFlags aFlags,
                                    std::vector<CapturedTiledPaintState::Copy>* aCopies,
                                    std::vector<RefPtr<TextureClient>>* aClients);
 };
 

--- a/gfx/thebes/gfxPlatform.cpp
+++ b/gfx/thebes/gfxPlatform.cpp
@@ -17,16 +17,17 @@
 #include "mozilla/gfx/GraphicsMessages.h"
 #include "mozilla/ClearOnShutdown.h"
 #include "mozilla/Telemetry.h"
 #include "mozilla/TimeStamp.h"
 #include "mozilla/Unused.h"
 
 #include "mozilla/Logging.h"
 #include "mozilla/Services.h"
+#include "nsAppDirectoryServiceDefs.h"
 
 #include "gfxCrashReporterUtils.h"
 #include "gfxPlatform.h"
 #include "gfxPrefs.h"
 #include "gfxEnv.h"
 #include "gfxTextRun.h"
 #include "gfxUserFontSet.h"
 #include "gfxConfig.h"
@@ -861,16 +862,28 @@ gfxPlatform::Init()
       Preferences::Unlock(FONT_VARIATIONS_PREF);
       if (!gPlatform->HasVariationFontSupport()) {
         // Ensure variation fonts are disabled and the pref is locked.
         Preferences::SetBool(FONT_VARIATIONS_PREF, false,
                              PrefValueKind::Default);
         Preferences::SetBool(FONT_VARIATIONS_PREF, false);
         Preferences::Lock(FONT_VARIATIONS_PREF);
       }
+
+      nsCOMPtr<nsIFile> profDir;
+      rv = NS_GetSpecialDirectory(NS_APP_PROFILE_DIR_STARTUP, getter_AddRefs(profDir));
+      if (NS_FAILED(rv)) {
+        gfxVars::SetProfDirectory(nsString());
+      } else {
+        nsAutoString path;
+        profDir->GetPath(path);
+        gfxVars::SetProfDirectory(nsString(path));
+      }
+
+      gfxUtils::RemoveShaderCacheFromDiskIfNecessary();
     }
 
     if (obs) {
       obs->NotifyObservers(nullptr, "gfx-features-ready", nullptr);
     }
 }
 
 /* static*/ bool
@@ -2621,17 +2634,20 @@ gfxPlatform::InitWebRenderConfig()
         NS_LITERAL_CSTRING("FEATURE_FAILURE_ANGLE_DISABLED"));
     } else {
       gfxVars::SetUseWebRenderANGLE(gfxConfig::IsEnabled(Feature::WEBRENDER));
     }
   }
 #endif
 
   if (Preferences::GetBool("gfx.webrender.program-binary", false)) {
-    gfx::gfxVars::SetUseWebRenderProgramBinary(gfxConfig::IsEnabled(Feature::WEBRENDER));
+    gfxVars::SetUseWebRenderProgramBinary(gfxConfig::IsEnabled(Feature::WEBRENDER));
+    if (Preferences::GetBool("gfx.webrender.program-binary-disk", false)) {
+      gfxVars::SetUseWebRenderProgramBinaryDisk(gfxConfig::IsEnabled(Feature::WEBRENDER));
+    }
   }
 
 #ifdef MOZ_WIDGET_ANDROID
   featureWebRender.ForceDisable(
     FeatureStatus::Unavailable,
     "WebRender not ready for use on Android",
     NS_LITERAL_CSTRING("FEATURE_FAILURE_ANDROID"));
 #endif

--- a/gfx/thebes/gfxUtils.cpp
+++ b/gfx/thebes/gfxUtils.cpp
@@ -17,21 +17,24 @@
 #include "mozilla/dom/ImageEncoder.h"
 #include "mozilla/dom/WorkerPrivate.h"
 #include "mozilla/dom/WorkerRunnable.h"
 #include "mozilla/gfx/2D.h"
 #include "mozilla/gfx/DataSurfaceHelpers.h"
 #include "mozilla/gfx/Logging.h"
 #include "mozilla/gfx/PathHelpers.h"
 #include "mozilla/gfx/Swizzle.h"
+#include "mozilla/gfx/gfxVars.h"
 #include "mozilla/Maybe.h"
 #include "mozilla/RefPtr.h"
 #include "mozilla/UniquePtrExtensions.h"
 #include "mozilla/Unused.h"
 #include "mozilla/Vector.h"
+#include "mozilla/webrender/webrender_ffi.h"
+#include "nsAppRunner.h"
 #include "nsComponentManagerUtils.h"
 #include "nsIClipboardHelper.h"
 #include "nsIFile.h"
 #include "nsIGfxInfo.h"
 #include "nsIPresShell.h"
 #include "nsPresContext.h"
 #include "nsRegion.h"
 #include "nsServiceManagerUtils.h"
@@ -1463,16 +1466,64 @@ gfxUtils::ThreadSafeGetFeatureStatus(con
     }
 
     return runnable->GetNSResult();
   }
 
   return gfxInfo->GetFeatureStatus(feature, failureId, status);
 }
 
+#define GFX_SHADER_CHECK_BUILD_VERSION_PREF "gfx-shader-check.build-version"
+#define GFX_SHADER_CHECK_DEVICE_ID_PREF "gfx-shader-check.device-id"
+#define GFX_SHADER_CHECK_DRIVER_VERSION_PREF "gfx-shader-check.driver-version"
+
+/* static */ void
+gfxUtils::RemoveShaderCacheFromDiskIfNecessary()
+{
+  if (!gfxVars::UseWebRenderProgramBinaryDisk()) {
+    return;
+  }
+
+  nsCOMPtr<nsIGfxInfo> gfxInfo = services::GetGfxInfo();
+
+  // Get current values
+  nsCString buildID(mozilla::PlatformBuildID());
+  nsString deviceID, driverVersion;
+  gfxInfo->GetAdapterDeviceID(deviceID);
+  gfxInfo->GetAdapterDriverVersion(driverVersion);
+
+  // Get pref stored values
+  nsAutoCString buildIDChecked;
+  Preferences::GetCString(GFX_SHADER_CHECK_BUILD_VERSION_PREF, buildIDChecked);
+  nsAutoString deviceIDChecked, driverVersionChecked;
+  Preferences::GetString(GFX_SHADER_CHECK_DEVICE_ID_PREF, deviceIDChecked);
+  Preferences::GetString(GFX_SHADER_CHECK_DRIVER_VERSION_PREF, driverVersionChecked);
+
+  if (buildID == buildIDChecked &&
+      deviceID == deviceIDChecked &&
+      driverVersion == driverVersionChecked) {
+      return;
+  }
+
+  nsAutoString path(gfx::gfxVars::ProfDirectory());
+
+  if (!wr::remove_program_binary_disk_cache(&path)) {
+    // Failed to remove program binary disk cache. The disk cache might have
+    // invalid data. Disable program binary disk cache usage.
+    gfxVars::SetUseWebRenderProgramBinaryDisk(false);
+    return;
+  }
+
+  Preferences::SetCString(GFX_SHADER_CHECK_BUILD_VERSION_PREF, buildID);
+  Preferences::SetString(GFX_SHADER_CHECK_DEVICE_ID_PREF, deviceID);
+  Preferences::SetString(GFX_SHADER_CHECK_DRIVER_VERSION_PREF, driverVersion);
+  return;
+}
+
+
 /* static */ bool
 gfxUtils::DumpDisplayList() {
   return gfxPrefs::LayoutDumpDisplayList() ||
          (gfxPrefs::LayoutDumpDisplayListParent() && XRE_IsParentProcess()) ||
          (gfxPrefs::LayoutDumpDisplayListContent() && XRE_IsContentProcess());
 }
 
 FILE *gfxUtils::sDumpPaintFile = stderr;

--- a/gfx/thebes/gfxUtils.h
+++ b/gfx/thebes/gfxUtils.h
@@ -290,16 +290,18 @@ public:
                                    const char16_t* aEncoderOptions,
                                    nsIInputStream** outStream);
 
     static nsresult ThreadSafeGetFeatureStatus(const nsCOMPtr<nsIGfxInfo>& gfxInfo,
                                                int32_t feature,
                                                nsACString& failureId,
                                                int32_t* status);
 
+    static void RemoveShaderCacheFromDiskIfNecessary();
+
     /**
      * Copy to the clipboard as a PNG encoded Data URL.
      */
     static void CopyAsDataURI(SourceSurface* aSourceSurface);
     static void CopyAsDataURI(DrawTarget* aDT);
 
     static bool DumpDisplayList();
 

--- a/gfx/webrender_bindings/Cargo.toml
+++ b/gfx/webrender_bindings/Cargo.toml
@@ -6,22 +6,26 @@ license = "MPL-2.0"
 
 [dependencies]
 rayon = "1"
 thread_profiler = "0.1.1"
 euclid = { version = "0.17", features = ["serde"] }
 app_units = "0.6"
 gleam = "0.5"
 log = "0.4"
+nsstring = { path = "../../servo/support/gecko/nsstring" }
+bincode = "1.0"
+uuid = {version = "0.1.18"}
+fxhash = "0.2.1"
 
 [dependencies.webrender]
 path = "../webrender"
 version = "0.57.2"
 default-features = false
-features = ["capture"]
+features = ["capture", "serialize_program"]
 
 [target.'cfg(target_os = "windows")'.dependencies]
 dwrote = "0.4.1"
 
 [target.'cfg(target_os = "macos")'.dependencies]
 core-foundation = "0.5"
 core-graphics = "0.13"
 foreign-types = "0.3.0"

--- a/gfx/webrender_bindings/RenderThread.cpp
+++ b/gfx/webrender_bindings/RenderThread.cpp
@@ -65,16 +65,26 @@ RenderThread::Start()
     return;
   }
 
   sRenderThread = new RenderThread(thread);
 #ifdef XP_WIN
   widget::WinCompositorWindowThread::Start();
 #endif
   layers::SharedSurfacesParent::Initialize();
+
+  if (XRE_IsGPUProcess() &&
+      gfx::gfxVars::UseWebRenderProgramBinary()) {
+    MOZ_ASSERT(gfx::gfxVars::UseWebRender());
+    // Initialize program cache if necessary
+    RefPtr<Runnable> runnable = WrapRunnable(
+      RefPtr<RenderThread>(sRenderThread.get()),
+      &RenderThread::ProgramCacheTask);
+    sRenderThread->Loop()->PostTask(runnable.forget());
+  }
 }
 
 // static
 void
 RenderThread::ShutDown()
 {
   MOZ_ASSERT(NS_IsMainThread());
   MOZ_ASSERT(sRenderThread);
@@ -506,40 +516,53 @@ RenderThread::GetRenderTexture(wr::WrExt
 {
   MOZ_ASSERT(IsInRenderThread());
 
   MutexAutoLock lock(mRenderTextureMapLock);
   MOZ_ASSERT(mRenderTextures.GetWeak(aExternalImageId.mHandle));
   return mRenderTextures.GetWeak(aExternalImageId.mHandle);
 }
 
+void
+RenderThread::ProgramCacheTask()
+{
+  ProgramCache();
+}
+
 WebRenderProgramCache*
 RenderThread::ProgramCache()
 {
   MOZ_ASSERT(IsInRenderThread());
 
   if (!mProgramCache) {
-    mProgramCache = MakeUnique<WebRenderProgramCache>();
+    mProgramCache = MakeUnique<WebRenderProgramCache>(ThreadPool().Raw());
   }
   return mProgramCache.get();
 }
 
 WebRenderThreadPool::WebRenderThreadPool()
 {
   mThreadPool = wr_thread_pool_new();
 }
 
 WebRenderThreadPool::~WebRenderThreadPool()
 {
   wr_thread_pool_delete(mThreadPool);
 }
 
-WebRenderProgramCache::WebRenderProgramCache()
+WebRenderProgramCache::WebRenderProgramCache(wr::WrThreadPool* aThreadPool)
 {
-  mProgramCache = wr_program_cache_new();
+  MOZ_ASSERT(aThreadPool);
+
+  nsAutoString path;
+  if (gfxVars::UseWebRenderProgramBinaryDisk()) {
+    path.Append(gfx::gfxVars::ProfDirectory());
+  }
+  mProgramCache = wr_program_cache_new(&path, aThreadPool);
+  wr_try_load_shader_from_disk(mProgramCache);
 }
 
 WebRenderProgramCache::~WebRenderProgramCache()
 {
   wr_program_cache_delete(mProgramCache);
 }
 
 } // namespace wr

--- a/gfx/webrender_bindings/RenderThread.h
+++ b/gfx/webrender_bindings/RenderThread.h
@@ -37,17 +37,17 @@ public:
   wr::WrThreadPool* Raw() { return mThreadPool; }
 
 protected:
   wr::WrThreadPool* mThreadPool;
 };
 
 class WebRenderProgramCache {
 public:
-  WebRenderProgramCache();
+  explicit WebRenderProgramCache(wr::WrThreadPool* aThreadPool);
 
   ~WebRenderProgramCache();
 
   wr::WrProgramCache* Raw() { return mProgramCache; }
 
 protected:
   wr::WrProgramCache* mProgramCache;
 };
@@ -165,16 +165,17 @@ public:
   /// Can only be called from the render thread.
   WebRenderProgramCache* ProgramCache();
 
 private:
   explicit RenderThread(base::Thread* aThread);
 
   void DeferredRenderTextureHostDestroy(RefPtr<RenderTextureHost> aTexture);
   void ShutDownTask(layers::SynchronousTask* aTask);
+  void ProgramCacheTask();
 
   ~RenderThread();
 
   base::Thread* const mThread;
 
   WebRenderThreadPool mThreadPool;
   UniquePtr<WebRenderProgramCache> mProgramCache;
 

--- a/gfx/webrender_bindings/src/bindings.rs
+++ b/gfx/webrender_bindings/src/bindings.rs
@@ -8,22 +8,24 @@ use std::os::raw::{c_void, c_char, c_flo
 use gleam::gl;
 
 use webrender::api::*;
 use webrender::{ReadPixelsFormat, Renderer, RendererOptions, ThreadListener};
 use webrender::{ExternalImage, ExternalImageHandler, ExternalImageSource};
 use webrender::DebugFlags;
 use webrender::{ApiRecordingReceiver, BinaryRecorder};
 use webrender::{AsyncPropertySampler, PipelineInfo, SceneBuilderHooks};
-use webrender::{ProgramCache, UploadMethod, VertexUsageHint};
+use webrender::{UploadMethod, VertexUsageHint};
 use thread_profiler::register_thread_with_profiler;
 use moz2d_renderer::Moz2dImageRenderer;
+use program_cache::{WrProgramCache, remove_disk_cache};
 use app_units::Au;
 use rayon;
 use euclid::SideOffsets2D;
+use nsstring::nsAString;
 
 #[cfg(target_os = "windows")]
 use dwrote::{FontDescriptor, FontWeight, FontStretch, FontStyle};
 
 #[cfg(target_os = "macos")]
 use core_foundation::string::CFString;
 #[cfg(target_os = "macos")]
 use core_graphics::font::CGFont;
@@ -822,33 +824,50 @@ pub unsafe extern "C" fn wr_thread_pool_
 }
 
 /// cbindgen:postfix=WR_DESTRUCTOR_SAFE_FUNC
 #[no_mangle]
 pub unsafe extern "C" fn wr_thread_pool_delete(thread_pool: *mut WrThreadPool) {
     Box::from_raw(thread_pool);
 }
 
-pub struct WrProgramCache(Rc<ProgramCache>);
-
 #[no_mangle]
-pub unsafe extern "C" fn wr_program_cache_new() -> *mut WrProgramCache {
-    let program_cache = ProgramCache::new(None);
-    Box::into_raw(Box::new(WrProgramCache(program_cache)))
+pub unsafe extern "C" fn wr_program_cache_new(prof_path: &nsAString, thread_pool: *mut WrThreadPool) -> *mut WrProgramCache {
+    let workers = &(*thread_pool).0;
+    let program_cache = WrProgramCache::new(prof_path, workers);
+    Box::into_raw(Box::new(program_cache))
 }
 
 /// cbindgen:postfix=WR_DESTRUCTOR_SAFE_FUNC
 #[no_mangle]
 pub unsafe extern "C" fn wr_program_cache_delete(program_cache: *mut WrProgramCache) {
-    Rc::from_raw(program_cache);
+    Box::from_raw(program_cache);
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn wr_try_load_shader_from_disk(program_cache: *mut WrProgramCache) {
+    if !program_cache.is_null() {
+        (*program_cache).try_load_from_disk();
+    }
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn remove_program_binary_disk_cache(prof_path: &nsAString) -> bool {
+    match remove_disk_cache(prof_path) {
+        Ok(_) => true,
+        Err(_) => {
+            error!("Failed to remove program binary disk cache");
+            false
+        }
+    }
 }
 
 #[no_mangle]
 pub extern "C" fn wr_renderer_update_program_cache(renderer: &mut Renderer, program_cache: &mut WrProgramCache) {
-    let program_cache = Rc::clone(&program_cache.0);
+    let program_cache = Rc::clone(&program_cache.rc_get());
     renderer.update_program_cache(program_cache);
 }
 
 // Call MakeCurrent before this.
 #[no_mangle]
 pub extern "C" fn wr_window_new(window_id: WrWindowId,
                                 window_width: u32,
                                 window_height: u32,

--- a/gfx/webrender_bindings/src/lib.rs
+++ b/gfx/webrender_bindings/src/lib.rs
@@ -3,27 +3,34 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #![deny(warnings)]
 
 extern crate webrender;
 extern crate euclid;
 extern crate app_units;
 extern crate gleam;
+extern crate nsstring;
 extern crate rayon;
 extern crate thread_profiler;
+extern crate bincode;
+extern crate uuid;
+extern crate fxhash;
 
 #[macro_use]
 extern crate log;
 
 #[cfg(target_os = "windows")]
 extern crate dwrote;
 
+
 #[cfg(target_os = "macos")]
 extern crate core_foundation;
 #[cfg(target_os = "macos")]
 extern crate core_graphics;
 #[cfg(target_os = "macos")]
 extern crate foreign_types;
 
+mod program_cache;
+
 #[allow(non_snake_case)]
 pub mod bindings;
 pub mod moz2d_renderer;

new file mode 100644
--- /dev/null
+++ b/gfx/webrender_bindings/src/program_cache.rs
@@ -0,0 +1,298 @@
+use std::cell::RefCell;
+use std::io::{Error, ErrorKind};
+use std::fs::{File, create_dir_all, read_dir};
+use std::io::{Read, Write};
+use std::path::{PathBuf};
+use std::rc::Rc;
+use std::sync::Arc;
+
+use webrender::{ProgramBinary, ProgramCache, ProgramCacheObserver};
+use bincode;
+use fxhash;
+use nsstring::nsAString;
+use rayon::ThreadPool;
+use uuid::Uuid;
+
+const MAX_LOAD_TIME_MS: u64 = 400;
+const MAX_CACHED_PROGRAM_COUNT: u32 = 15;
+
+fn deserialize_program_binary(path: &PathBuf) -> Result<Arc<ProgramBinary>, Error> {
+    let mut buf = vec![];
+    let mut file = File::open(path)?;
+    file.read_to_end(&mut buf)?;
+
+    if buf.len() <= 8 {
+        return Err(Error::new(ErrorKind::InvalidData, "File size is too small"));
+    }
+    let hash = &buf[0 .. 8];
+    let data = &buf[8 ..];
+
+    // Check if hash is correct
+    let hash:u64 = bincode::deserialize(&hash).unwrap();
+    let hash_data = fxhash::hash64(&data);
+    if hash != hash_data {
+        return Err(Error::new(ErrorKind::InvalidData, "File data is invalid"));
+    }
+
+    // Deserialize ProgramBinary
+    let binary = match bincode::deserialize(&data) {
+        Ok(binary) => binary,
+        Err(_) => return Err(Error::new(ErrorKind::InvalidData, "Failed to deserialize ProgramBinary")),
+    };
+
+    Ok(Arc::new(binary))
+}
+
+#[cfg(target_os = "windows")]
+fn get_cache_path_from_prof_path(prof_path: &nsAString) -> Option<PathBuf> {
+    if prof_path.is_empty() {
+        // Empty means that we do not use disk cache.
+        return None;
+    }
+
+    use std::ffi::OsString;
+    use std::os::windows::prelude::*;
+
+    let prof_path = OsString::from_wide(prof_path.as_ref());
+    let mut cache_path = PathBuf::from(&prof_path);
+    cache_path.push("shader-cache");
+
+    Some(cache_path)
+}
+
+#[cfg(not(target_os="windows"))]
+fn get_cache_path_from_prof_path(_prof_path: &nsAString) -> Option<PathBuf> {
+    // Not supported yet.
+    None
+}
+
+struct WrProgramBinaryDiskCache {
+    cache_path: Option<PathBuf>,
+    program_count: u32,
+    is_enabled: bool,
+    workers: Arc<ThreadPool>,
+}
+
+impl WrProgramBinaryDiskCache {
+    #[allow(dead_code)]
+    fn new(prof_path: &nsAString, workers: &Arc<ThreadPool>) -> Self {
+        let cache_path = get_cache_path_from_prof_path(prof_path);
+        let is_enabled = cache_path.is_some();
+        let workers = Arc::clone(workers);
+
+        WrProgramBinaryDiskCache{
+            cache_path,
+            program_count: 0,
+            is_enabled,
+            workers,
+        }
+    }
+
+    fn notify_binary_added(&mut self, program_binary: &Arc<ProgramBinary>) {
+        if !self.is_enabled {
+            return;
+        }
+
+        if let Some(ref cache_path) = self.cache_path {
+            if let Err(_) = create_dir_all(&cache_path) {
+                error!("failed to create dir for shader disk cache");
+                return;
+            }
+
+            self.program_count += 1;
+            if self.program_count > MAX_CACHED_PROGRAM_COUNT {
+                // Disable disk cache to avoid storing more shader programs to disk
+                self.is_enabled = false;
+                return;
+            }
+
+            // Use uuid for file name
+            let uuid1 = Uuid::new_v4();
+            let file_name = uuid1.to_hyphenated_string();
+            let program_binary = Arc::clone(program_binary);
+            let file_path = cache_path.join(&file_name);
+
+            let program_count = self.program_count;
+
+            // Save to disk on worker thread
+            self.workers.spawn(move || {
+
+                use std::time::{Instant};
+                let start = Instant::now();
+
+                let data: Vec<u8> = match bincode::serialize(&*program_binary) {
+                    Ok(data) => data,
+                    Err(err) => {
+                        error!("Failed to serialize program binary error: {}", err);
+                        return;
+                    }
+                };
+
+                let mut file = match File::create(&file_path) {
+                    Ok(file) => file,
+                    Err(err) => {
+                        error!("Unable to create file for program binary error: {}", err);
+                        return;
+                    }
+                };
+
+                // Write hash
+                let hash = fxhash::hash64(&data);
+                let hash = bincode::serialize(&hash).unwrap();
+                assert!(hash.len() == 8);
+                match file.write_all(&hash) {
+                    Err(err) => {
+                        error!("Failed to write hash to file error: {}", err);
+                    }
+                    _ => {},
+                };
+
+                // Write serialized data
+                match file.write_all(&data) {
+                    Err(err) => {
+                        error!("Failed to write program binary to file error: {}", err);
+                    }
+                    _ => {},
+                };
+
+                let elapsed = start.elapsed();
+                info!("notify_binary_added: {} ms program_count {}",
+                    (elapsed.as_secs() * 1_000) + (elapsed.subsec_nanos() / 1_000_000) as u64, program_count);
+
+            });
+        }
+    }
+
+    pub fn try_load_from_disk(&mut self, program_cache: &Rc<ProgramCache>) {
+        if !self.is_enabled {
+            return;
+        }
+
+        if let Some(ref cache_path) = self.cache_path {
+            use std::time::{Instant};
+            let start = Instant::now();
+
+            // Load program binaries if exist
+            if cache_path.exists() && cache_path.is_dir() {
+                for entry in read_dir(cache_path).unwrap() {
+                    let entry = entry.unwrap();
+                    let path = entry.path();
+
+                    info!("loading shader file");
+
+                    match deserialize_program_binary(&path) {
+                        Ok(program) => {
+                            program_cache.load_program_binary(program);
+                        }
+                        Err(err) => {
+                            error!("Failed to desriralize program binary error: {}", err);
+                        }
+                    };
+
+                    self.program_count += 1;
+
+                    let elapsed = start.elapsed();
+                    let elapsed_ms = (elapsed.as_secs() * 1_000) + (elapsed.subsec_nanos() / 1_000_000) as u64;
+                    info!("deserialize_program_binary: {} ms program_count {}", elapsed_ms, self.program_count);
+
+                    if self.program_count > MAX_CACHED_PROGRAM_COUNT || elapsed_ms > MAX_LOAD_TIME_MS {
+                        // Disable disk cache to avoid storing more shader programs to disk
+                        self.is_enabled = false;
+                        break;
+                    }
+                }
+            }
+        }
+    }
+}
+
+pub struct WrProgramCacheObserver {
+    disk_cache: Rc<RefCell<WrProgramBinaryDiskCache>>,
+}
+
+impl WrProgramCacheObserver {
+    #[allow(dead_code)]
+    fn new(disk_cache: Rc<RefCell<WrProgramBinaryDiskCache>>) -> Self {
+        WrProgramCacheObserver{
+            disk_cache,
+        }
+    }
+}
+
+impl ProgramCacheObserver for WrProgramCacheObserver {
+    fn notify_binary_added(&self, program_binary: &Arc<ProgramBinary>) {
+        self.disk_cache.borrow_mut().notify_binary_added(program_binary);
+    }
+
+    fn notify_program_binary_failed(&self, _program_binary: &Arc<ProgramBinary>) {
+        error!("Failed program_binary");
+    }
+}
+
+
+pub struct WrProgramCache {
+    program_cache: Rc<ProgramCache>,
+    disk_cache: Option<Rc<RefCell<WrProgramBinaryDiskCache>>>,
+}
+
+impl WrProgramCache {
+    #[cfg(target_os = "windows")]
+    pub fn new(prof_path: &nsAString, workers: &Arc<ThreadPool>) -> Self {
+        let disk_cache = Rc::new(RefCell::new(WrProgramBinaryDiskCache::new(prof_path, workers)));
+        let program_cache_observer = Box::new(WrProgramCacheObserver::new(Rc::clone(&disk_cache)));
+        let program_cache = ProgramCache::new(Some(program_cache_observer));
+
+        WrProgramCache {
+            program_cache,
+            disk_cache: Some(disk_cache),
+        }
+    }
+
+    #[cfg(not(target_os="windows"))]
+    pub fn new(_prof_path: &nsAString, _: &Arc<ThreadPool>) -> Self {
+        let program_cache = ProgramCache::new(None);
+
+        WrProgramCache {
+            program_cache,
+            disk_cache: None,
+        }
+    }
+
+    pub fn rc_get(&self) -> &Rc<ProgramCache> {
+        &self.program_cache
+    }
+
+    pub fn try_load_from_disk(&self) {
+        if let Some(ref disk_cache) = self.disk_cache {
+            disk_cache.borrow_mut().try_load_from_disk(&self.program_cache);
+        } else {
+            error!("Shader disk cache is not supported");
+        }
+    }
+}
+
+#[cfg(target_os = "windows")]
+pub fn remove_disk_cache(prof_path: &nsAString) -> Result<(), Error> {
+    use std::fs::remove_dir_all;
+    use std::time::{Instant};
+
+    if let Some(cache_path) = get_cache_path_from_prof_path(prof_path) {
+        if cache_path.exists() {
+            let start = Instant::now();
+
+            remove_dir_all(&cache_path)?;
+
+            let elapsed = start.elapsed();
+            let elapsed_ms = (elapsed.as_secs() * 1_000) + (elapsed.subsec_nanos() / 1_000_000) as u64;
+            info!("remove_disk_cache: {} ms", elapsed_ms);
+        }
+    }
+    Ok(())
+}
+
+#[cfg(not(target_os="windows"))]
+pub fn remove_disk_cache(_prof_path: &nsAString) -> Result<(), Error> {
+    error!("Shader disk cache is not supported");
+    return Err(Error::new(ErrorKind::Other, "Not supported"))
+}
+

--- a/gfx/webrender_bindings/webrender_ffi_generated.h
+++ b/gfx/webrender_bindings/webrender_ffi_generated.h
@@ -12,16 +12,20 @@
  */
 
 #include <cstdint>
 #include <cstdlib>
 
 namespace mozilla {
 namespace wr {
 
+static const uint32_t MAX_CACHED_PROGRAM_COUNT = 15;
+
+static const uint64_t MAX_LOAD_TIME_MS = 400;
+
 enum class BorderStyle : uint32_t {
   None = 0,
   Solid = 1,
   Double = 2,
   Dotted = 3,
   Dashed = 4,
   Hidden = 5,
   Groove = 6,
@@ -996,16 +1000,20 @@ extern bool is_glcontext_egl(void *aGlco
 
 extern bool is_in_compositor_thread();
 
 extern bool is_in_main_thread();
 
 extern bool is_in_render_thread();
 
 WR_INLINE
+bool remove_program_binary_disk_cache(const nsAString *aProfPath)
+WR_FUNC;
+
+WR_INLINE
 const VecU8 *wr_add_ref_arc(const ArcVecU8 *aArc)
 WR_FUNC;
 
 WR_INLINE
 void wr_api_capture(DocumentHandle *aDh,
                     const char *aPath,
                     uint32_t aBitsRaw)
 WR_FUNC;
@@ -1406,17 +1414,18 @@ WR_INLINE
 void wr_pipeline_info_delete(WrPipelineInfo aInfo)
 WR_DESTRUCTOR_SAFE_FUNC;
 
 WR_INLINE
 void wr_program_cache_delete(WrProgramCache *aProgramCache)
 WR_DESTRUCTOR_SAFE_FUNC;
 
 WR_INLINE
-WrProgramCache *wr_program_cache_new()
+WrProgramCache *wr_program_cache_new(const nsAString *aProfPath,
+                                     WrThreadPool *aThreadPool)
 WR_FUNC;
 
 WR_INLINE
 bool wr_renderer_current_epoch(Renderer *aRenderer,
                                WrPipelineId aPipelineId,
                                WrEpoch *aOutEpoch)
 WR_FUNC;
 
@@ -1658,16 +1667,20 @@ WR_FUNC;
 
 WR_INLINE
 void wr_transaction_update_epoch(Transaction *aTxn,
                                  WrPipelineId aPipelineId,
                                  WrEpoch aEpoch)
 WR_FUNC;
 
 WR_INLINE
+void wr_try_load_shader_from_disk(WrProgramCache *aProgramCache)
+WR_FUNC;
+
+WR_INLINE
 void wr_vec_u8_free(WrVecU8 aV)
 WR_FUNC;
 
 WR_INLINE
 void wr_vec_u8_push_bytes(WrVecU8 *aV,
                           ByteSlice aBytes)
 WR_FUNC;
 

--- a/ipc/glue/IPCStream.ipdlh
+++ b/ipc/glue/IPCStream.ipdlh
@@ -29,16 +29,18 @@ struct IPCRemoteStream
 {
   // If this is true, the stream will send data only when the first operation
   // is done on the destination side. The benefit of this is that we do not
   // send data if not needed. On the other hand, it could have a performance
   // issue.
   bool delayedStart;
 
   IPCRemoteStreamType stream;
+
+  int64_t length;
 };
 
 // Use IPCStream or OptionalIPCStream in your ipdl to represent serialized
 // nsIInputStreams.  Then use AutoIPCStream from IPCStreamUtils.h to perform
 // the serialization.
 union IPCStream
 {
   InputStreamParamsWithFds;