--- a/browser/base/content/browser.js
+++ b/browser/base/content/browser.js
@@ -232,18 +232,17 @@ XPCOMUtils.defineLazyGetter(this, "Win7F
   return null;
 });
 
 var gBrowser;
 var gLastValidURLStr = "";
 var gInPrintPreviewMode = false;
 var gContextMenu = null; // nsContextMenu instance
 var gMultiProcessBrowser =
-  window.QueryInterface(Ci.nsIInterfaceRequestor)
-        .getInterface(Ci.nsIWebNavigation)
+  window.docShell
         .QueryInterface(Ci.nsILoadContext)
         .useRemoteTabs;
 
 if (AppConstants.platform != "macosx") {
   var gEditUIVisible = true;
 }
 
 /* globals gNavToolbox, gURLBar:true */
@@ -1233,19 +1232,17 @@ var gBrowserInit = {
     ToolbarIconColor.init();
   },
 
   onDOMContentLoaded() {
     gBrowser = window._gBrowser;
     delete window._gBrowser;
     gBrowser.init();
 
-    window.QueryInterface(Ci.nsIInterfaceRequestor)
-          .getInterface(Ci.nsIWebNavigation)
-          .QueryInterface(Ci.nsIDocShellTreeItem).treeOwner
+    window.docShell.treeOwner
           .QueryInterface(Ci.nsIInterfaceRequestor)
           .getInterface(Ci.nsIXULWindow)
           .XULBrowserWindow = window.XULBrowserWindow;
     window.QueryInterface(Ci.nsIDOMChromeWindow).browserDOMWindow =
       new nsBrowserAccess();
     BrowserWindowTracker.track(window);
 
     let initBrowser = gBrowser.initialBrowser;
@@ -1931,19 +1928,17 @@ var gBrowserInit = {
       WebAuthnPromptHelper.uninit();
       PanelUI.uninit();
       AutoShowBookmarksToolbar.uninit();
     }
 
     // Final window teardown, do this last.
     gBrowser.destroy();
     window.XULBrowserWindow = null;
-    window.QueryInterface(Ci.nsIInterfaceRequestor)
-          .getInterface(Ci.nsIWebNavigation)
-          .QueryInterface(Ci.nsIDocShellTreeItem).treeOwner
+    window.docShell.treeOwner
           .QueryInterface(Ci.nsIInterfaceRequestor)
           .getInterface(Ci.nsIXULWindow)
           .XULBrowserWindow = null;
     window.QueryInterface(Ci.nsIDOMChromeWindow).browserDOMWindow = null;
   },
 };
 
 function HandleAppCommandEvent(evt) {
@@ -2476,19 +2471,17 @@ function getPostDataStream(aPostDataStri
   let mimeStream = Cc["@mozilla.org/network/mime-input-stream;1"]
                      .createInstance(Ci.nsIMIMEInputStream);
   mimeStream.addHeader("Content-Type", aType);
   mimeStream.setData(dataStream);
   return mimeStream.QueryInterface(Ci.nsIInputStream);
 }
 
 function getLoadContext() {
-  return window.QueryInterface(Ci.nsIInterfaceRequestor)
-               .getInterface(Ci.nsIWebNavigation)
-               .QueryInterface(Ci.nsILoadContext);
+  return window.docShell.QueryInterface(Ci.nsILoadContext);
 }
 
 function readFromClipboard() {
   var url;
 
   try {
     // Create transferable that will transfer the text.
     var trans = Cc["@mozilla.org/widget/transferable;1"]
@@ -2548,19 +2541,17 @@ async function BrowserViewSourceOfDocume
     let doc = aArgsOrDocument;
     // Deprecated API - callers should pass args object instead.
     if (Cu.isCrossProcessWrapper(doc)) {
       throw new Error("BrowserViewSourceOfDocument cannot accept a CPOW " +
                       "as a document.");
     }
 
     let win = doc.defaultView;
-    let browser = win.getInterface(Ci.nsIWebNavigation)
-                     .QueryInterface(Ci.nsIDocShell)
-                     .chromeEventHandler;
+    let browser = win.docShell.chromeEventHandler;
     let outerWindowID = win.windowUtils.outerWindowID;
     let URL = browser.currentURI.spec;
     args = { browser, outerWindowID, URL };
   } else {
     args = aArgsOrDocument;
   }
 
   // Check if external view source is enabled.  If so, try it.  If it fails,

--- a/browser/base/content/content-refreshblocker.js
+++ b/browser/base/content/content-refreshblocker.js
@@ -155,19 +155,17 @@ var RefreshBlocker = {
     return false;
   },
 
   receiveMessage(message) {
     let data = message.data;
 
     if (message.name == "RefreshBlocker:Refresh") {
       let win = Services.wm.getOuterWindowWithId(data.outerWindowID);
-      let refreshURI = win.QueryInterface(Ci.nsIInterfaceRequestor)
-                          .getInterface(Ci.nsIDocShell)
-                          .QueryInterface(Ci.nsIRefreshURI);
+      let refreshURI = win.docShell.QueryInterface(Ci.nsIRefreshURI);
 
       let URI = Services.io.newURI(data.URI);
 
       refreshURI.forceRefreshURI(URI, null, data.delay, true);
     }
   },
 
   QueryInterface: ChromeUtils.generateQI([Ci.nsIWebProgressListener2, Ci.nsIWebProgressListener, Ci.nsISupportsWeakReference]),

--- a/browser/base/content/nsContextMenu.js
+++ b/browser/base/content/nsContextMenu.js
@@ -225,21 +225,17 @@ nsContextMenu.prototype = {
     this.targetSelectors = gContextMenuContentData
                            ? gContextMenuContentData.popupNodeSelectors
                            : [];
 
     if (this.isRemote) {
       this.browser = gContextMenuContentData.browser;
       this.selectionInfo = gContextMenuContentData.selectionInfo;
     } else {
-      this.browser = this.ownerDoc.defaultView
-                         .QueryInterface(Ci.nsIInterfaceRequestor)
-                         .getInterface(Ci.nsIWebNavigation)
-                         .QueryInterface(Ci.nsIDocShell)
-                         .chromeEventHandler;
+      this.browser = this.ownerDoc.defaultView.docShell.chromeEventHandler;
       this.selectionInfo = BrowserUtils.getSelectionDetails(window);
     }
 
     this.textSelected      = this.selectionInfo.text;
     this.isTextSelected    = this.textSelected.length != 0;
     this.webExtBrowserType = this.browser.getAttribute("webextension-view-type");
     this.inWebExtBrowser   = !!this.webExtBrowserType;
     this.inTabBrowser      = this.browser.ownerGlobal.gBrowser ?
@@ -255,18 +251,17 @@ nsContextMenu.prototype = {
       }
     }
 
     if (context.shouldInitInlineSpellCheckerUIWithChildren) {
       if (this.isRemote) {
         InlineSpellCheckerUI.initFromRemote(gContextMenuContentData.spellInfo);
       } else {
         var targetWin = this.ownerDoc.defaultView;
-        var editingSession = targetWin.QueryInterface(Ci.nsIInterfaceRequestor)
-                                      .getInterface(Ci.nsIWebNavigation)
+        var editingSession = targetWin.docShell
                                       .QueryInterface(Ci.nsIInterfaceRequestor)
                                       .getInterface(Ci.nsIEditingSession);
 
         InlineSpellCheckerUI.init(editingSession.getEditorForWindow(targetWin));
         InlineSpellCheckerUI.initFromEvent(document.popupRangeParent,
                                            document.popupRangeOffset);
       }
 

--- a/browser/base/content/pageinfo/pageInfo.js
+++ b/browser/base/content/pageinfo/pageInfo.js
@@ -233,19 +233,17 @@ const PREFERENCES_CONTRACTID    = "@mozi
 
 // a number of services I'll need later
 // the cache services
 const nsICacheStorageService = Ci.nsICacheStorageService;
 const nsICacheStorage = Ci.nsICacheStorage;
 const cacheService = Cc["@mozilla.org/netwerk/cache-storage-service;1"].getService(nsICacheStorageService);
 
 var loadContextInfo = Services.loadContextInfo.fromLoadContext(
-  window.QueryInterface(Ci.nsIInterfaceRequestor)
-        .getInterface(Ci.nsIWebNavigation)
-        .QueryInterface(Ci.nsILoadContext), false);
+  window.docShell.QueryInterface(Ci.nsILoadContext), false);
 var diskStorage = cacheService.diskCacheStorage(loadContextInfo, false);
 
 const nsICookiePermission  = Ci.nsICookiePermission;
 const nsIPermissionManager = Ci.nsIPermissionManager;
 
 const nsICertificateDialogs = Ci.nsICertificateDialogs;
 const CERTIFICATEDIALOGS_CONTRACTID = "@mozilla.org/nsCertificateDialogs;1";
 

--- a/browser/base/content/tabbrowser.js
+++ b/browser/base/content/tabbrowser.js
@@ -653,20 +653,17 @@ window._gBrowser = {
     return this._outerWindowIDBrowserMap.get(aID);
   },
 
   _getTabForContentWindow(aWindow) {
     // When not using remote browsers, we can take a fast path by getting
     // directly from the content window to the browser without looping
     // over all browsers.
     if (!gMultiProcessBrowser) {
-      let browser = aWindow.QueryInterface(Ci.nsIInterfaceRequestor)
-                           .getInterface(Ci.nsIWebNavigation)
-                           .QueryInterface(Ci.nsIDocShell)
-                           .chromeEventHandler;
+      let browser = aWindow.docShell.chromeEventHandler;
       return this.getTabForBrowser(browser);
     }
 
     for (let i = 0; i < this.browsers.length; i++) {
       // NB: We use contentWindowAsCPOW so that this code works both
       // for remote browsers as well. aWindow may be a CPOW.
       if (this.browsers[i].contentWindowAsCPOW == aWindow)
         return this.tabs[i];
@@ -3063,21 +3060,17 @@ window._gBrowser = {
     // immediately without animation before the docshell swap, to avoid
     // about:blank being painted.
     let [closeWindow] = aOtherTab._endRemoveArgs;
     if (closeWindow) {
       let win = aOtherTab.ownerGlobal;
       win.windowUtils.suppressAnimation(true);
       // Only suppressing window animations isn't enough to avoid
       // an empty content area being painted.
-      let baseWin = win.QueryInterface(Ci.nsIInterfaceRequestor)
-                       .getInterface(Ci.nsIDocShell)
-                       .QueryInterface(Ci.nsIDocShellTreeItem)
-                       .treeOwner
-                       .QueryInterface(Ci.nsIBaseWindow);
+      let baseWin = win.docShell.treeOwner.QueryInterface(Ci.nsIBaseWindow);
       baseWin.visibility = false;
     }
 
     let modifiedAttrs = [];
     if (aOtherTab.hasAttribute("muted")) {
       aOurTab.setAttribute("muted", "true");
       aOurTab.muteReason = aOtherTab.muteReason;
       ourBrowser.mute();

--- a/browser/base/content/test/general/browser_bug1297539.js
+++ b/browser/base/content/test/general/browser_bug1297539.js
@@ -13,19 +13,17 @@
  * "pasteTransferable" runs only in the content process.
  * This doesn't test the remote case.
  *
  */
 
 "use strict";
 
 function getLoadContext() {
-  return window.QueryInterface(Ci.nsIInterfaceRequestor)
-               .getInterface(Ci.nsIWebNavigation)
-               .QueryInterface(Ci.nsILoadContext);
+  return window.docShell.QueryInterface(Ci.nsILoadContext);
 }
 
 function getTransferableFromClipboard(asHTML) {
   let trans = Cc["@mozilla.org/widget/transferable;1"].
                     createInstance(Ci.nsITransferable);
   trans.init(getLoadContext());
   if (asHTML) {
     trans.addDataFlavor("text/html");

--- a/browser/base/content/test/performance/head.js
+++ b/browser/base/content/test/performance/head.js
@@ -52,20 +52,17 @@ async function recordReflows(testPromise
       // Interruptible reflows are the reflows caused by the refresh
       // driver ticking. These are fine.
     },
 
     QueryInterface: ChromeUtils.generateQI([Ci.nsIReflowObserver,
                                             Ci.nsISupportsWeakReference])
   };
 
-  let docShell = win.QueryInterface(Ci.nsIInterfaceRequestor)
-                    .getInterface(Ci.nsIWebNavigation)
-                    .QueryInterface(Ci.nsIDocShell);
-  docShell.addWeakReflowObserver(observer);
+  win.docShell.addWeakReflowObserver(observer);
 
   let dirtyFrameFn = event => {
     if (event.type != "MozAfterPaint") {
       dirtyFrame(win);
     }
   };
   Services.els.addListenerForAllEvents(win, dirtyFrameFn, true);
 

--- a/browser/base/content/test/siteIdentity/test_no_mcb_on_http_site_font.html
+++ b/browser/base/content/test/siteIdentity/test_no_mcb_on_http_site_font.html
@@ -7,21 +7,17 @@
 <head>
   <meta charset="utf-8">
   <title>Test 2 for Bug 909920</title>
   <link rel="stylesheet" type="text/css" href="https://example.com/browser/browser/base/content/test/siteIdentity/test_no_mcb_on_http_site_font.css" />
 <script type="application/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
 
 <script type="text/javascript">
   function checkLoadStates() {
-   var ui = SpecialPowers.wrap(window)
-            .QueryInterface(SpecialPowers.Ci.nsIInterfaceRequestor)
-             .getInterface(SpecialPowers.Ci.nsIWebNavigation)
-             .QueryInterface(SpecialPowers.Ci.nsIDocShell)
-             .securityUI;
+   var ui = SpecialPowers.wrap(window).docShell.securityUI;
 
    var loadedMixedActive = ui &&
      !!(ui.state & SpecialPowers.Ci.nsIWebProgressListener.STATE_LOADED_MIXED_ACTIVE_CONTENT);
    is(loadedMixedActive, false, "OK: Should not load mixed active content!");
 
    var blockedMixedActive = ui &&
      !!(ui.state & SpecialPowers.Ci.nsIWebProgressListener.STATE_BLOCKED_MIXED_ACTIVE_CONTENT);
    is(blockedMixedActive, false, "OK: Should not block mixed active content!");

--- a/browser/base/content/test/siteIdentity/test_no_mcb_on_http_site_font2.html
+++ b/browser/base/content/test/siteIdentity/test_no_mcb_on_http_site_font2.html
@@ -7,21 +7,17 @@
 <head>
   <meta charset="utf-8">
   <title>Test 3 for Bug 909920</title>
   <link rel="stylesheet" type="text/css" href="https://example.com/browser/browser/base/content/test/siteIdentity/test_no_mcb_on_http_site_font2.css" />
 <script type="application/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
 
 <script type="text/javascript">
   function checkLoadStates() {
-   var ui = SpecialPowers.wrap(window)
-        .QueryInterface(SpecialPowers.Ci.nsIInterfaceRequestor)
-             .getInterface(SpecialPowers.Ci.nsIWebNavigation)
-             .QueryInterface(SpecialPowers.Ci.nsIDocShell)
-             .securityUI;
+   var ui = SpecialPowers.wrap(window).docShell.securityUI;
 
    var loadedMixedActive = ui &&
      !!(ui.state & SpecialPowers.Ci.nsIWebProgressListener.STATE_LOADED_MIXED_ACTIVE_CONTENT);
    is(loadedMixedActive, false, "OK: Should not load mixed active content!");
 
    var blockedMixedActive = ui &&
      !!(ui.state & SpecialPowers.Ci.nsIWebProgressListener.STATE_BLOCKED_MIXED_ACTIVE_CONTENT);
    is(blockedMixedActive, false, "OK: Should not block mixed active content!");

--- a/browser/base/content/test/siteIdentity/test_no_mcb_on_http_site_img.html
+++ b/browser/base/content/test/siteIdentity/test_no_mcb_on_http_site_img.html
@@ -7,21 +7,17 @@
 <head>
   <meta charset="utf-8">
   <title>Test 1 for Bug 909920</title>
   <link rel="stylesheet" type="text/css" href="https://example.com/browser/browser/base/content/test/siteIdentity/test_no_mcb_on_http_site_img.css" />
 <script type="application/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
 
 <script type="text/javascript">
   function checkLoadStates() {
-   var ui = SpecialPowers.wrap(window)
-            .QueryInterface(SpecialPowers.Ci.nsIInterfaceRequestor)
-             .getInterface(SpecialPowers.Ci.nsIWebNavigation)
-             .QueryInterface(SpecialPowers.Ci.nsIDocShell)
-             .securityUI;
+   var ui = SpecialPowers.wrap(window).docShell.securityUI;
 
    var loadedMixedActive = ui &&
      !!(ui.state & SpecialPowers.Ci.nsIWebProgressListener.STATE_LOADED_MIXED_ACTIVE_CONTENT);
    is(loadedMixedActive, false, "OK: Should not load mixed active content!");
 
    var blockedMixedActive = ui &&
      !!(ui.state & SpecialPowers.Ci.nsIWebProgressListener.STATE_BLOCKED_MIXED_ACTIVE_CONTENT);
    is(blockedMixedActive, false, "OK: Should not block mixed active content!");

--- a/browser/components/customizableui/CustomizableUI.jsm
+++ b/browser/components/customizableui/CustomizableUI.jsm
@@ -1709,21 +1709,18 @@ var CustomizableUIInternal = {
     // a toolbarbutton/item, or the panel:
     while (true && target) {
       // Skip out of iframes etc:
       if (target.nodeType == target.DOCUMENT_NODE) {
         if (!target.defaultView) {
           // Err, we're done.
           break;
         }
-        // Cue some voodoo
-        target = target.defaultView.QueryInterface(Ci.nsIInterfaceRequestor)
-                                   .getInterface(Ci.nsIWebNavigation)
-                                   .QueryInterface(Ci.nsIDocShell)
-                                   .chromeEventHandler;
+        // Find containing browser or iframe element in the parent doc.
+        target = target.defaultView.docShell.chromeEventHandler;
         if (!target) {
           break;
         }
       }
       let tagName = target.localName;
       inInput = tagName == "input" || tagName == "textbox";
       inItem = tagName == "toolbaritem" || tagName == "toolbarbutton";
       let isMenuItem = tagName == "menuitem";

--- a/browser/components/downloads/DownloadsTaskbar.jsm
+++ b/browser/components/downloads/DownloadsTaskbar.jsm
@@ -117,19 +117,17 @@ var DownloadsTaskbar = {
     }
   },
 
   /**
    * On Windows, attaches the taskbar indicator to the specified browser window.
    */
   _attachIndicator(aWindow) {
     // Activate the indicator on the specified window.
-    let docShell = aWindow.QueryInterface(Ci.nsIInterfaceRequestor)
-                          .getInterface(Ci.nsIWebNavigation)
-                          .QueryInterface(Ci.nsIDocShellTreeItem).treeOwner
+    let docShell = aWindow.docShell.treeOwner
                           .QueryInterface(Ci.nsIInterfaceRequestor)
                           .getInterface(Ci.nsIXULWindow).docShell;
     this._taskbarProgress = gWinTaskbar.getTaskbarProgress(docShell);
 
     // If the DownloadSummary object has already been created, we should update
     // the state of the new indicator, otherwise it will be updated as soon as
     // the DownloadSummary view is registered.
     if (this._summary) {

--- a/browser/components/extensions/test/browser/browser_ext_find.js
+++ b/browser/components/extensions/test/browser/browser_ext_find.js
@@ -1,17 +1,15 @@
 /* global browser */
 "use strict";
 
 function frameScript() {
   function getSelectedText() {
     let frame = this.content.frames[0].frames[1];
-    let docShell = frame.QueryInterface(Ci.nsIInterfaceRequestor)
-                        .getInterface(Ci.nsIWebNavigation)
-                        .QueryInterface(Ci.nsIDocShell);
+    let docShell = frame.docShell;
     let controller = docShell.QueryInterface(Ci.nsIInterfaceRequestor)
                              .getInterface(Ci.nsISelectionDisplay)
                              .QueryInterface(Ci.nsISelectionController);
     let selection = controller.getSelection(controller.SELECTION_FIND);
     let range = selection.getRangeAt(0);
     let scope = {};
     ChromeUtils.import("resource://gre/modules/FindContent.jsm", scope);
     let highlighter = (new scope.FindContent(docShell)).highlighter;

--- a/browser/components/extensions/test/browser/browser_ext_windows_create.js
+++ b/browser/components/extensions/test/browser/browser_ext_windows_create.js
@@ -113,18 +113,17 @@ add_task(async function testWindowCreate
     }
     if (expected.hiddenChrome) {
       let chromeHidden = latestWindow.document.documentElement.getAttribute("chromehidden");
       is(chromeHidden.trim().split(/\s+/).sort().join(" "),
          expected.hiddenChrome.sort().join(" "),
          "Got expected hidden chrome");
     }
     if (expected.chromeFlags) {
-      let {chromeFlags} = latestWindow.QueryInterface(Ci.nsIInterfaceRequestor)
-                                      .getInterface(Ci.nsIDocShell)
+      let {chromeFlags} = latestWindow.docShell
                                       .treeOwner.QueryInterface(Ci.nsIInterfaceRequestor)
                                       .getInterface(Ci.nsIXULWindow);
       for (let flag of expected.chromeFlags) {
         ok(chromeFlags & Ci.nsIWebBrowserChrome[flag],
            `Expected window to have the ${flag} flag`);
       }
     }
 

--- a/browser/components/feeds/FeedWriter.js
+++ b/browser/components/feeds/FeedWriter.js
@@ -71,18 +71,17 @@ function FeedWriter() {
   this._selectedApp = undefined;
   this._selectedAppMenuItem = null;
   this._subscribeCallback = null;
   this._defaultHandlerMenuItem = null;
 
   Services.telemetry.scalarAdd("browser.feeds.preview_loaded", 1);
 
   XPCOMUtils.defineLazyGetter(this, "_mm", () =>
-    this._window.QueryInterface(Ci.nsIInterfaceRequestor).
-                 getInterface(Ci.nsIDocShell).
+    this._window.docShell.
                  QueryInterface(Ci.nsIInterfaceRequestor).
                  getInterface(Ci.nsIContentFrameMessageManager));
 }
 
 FeedWriter.prototype = {
   _getPropertyAsBag(container, property) {
     return container.fields.getProperty(property).
                      QueryInterface(Ci.nsIPropertyBag2);
@@ -705,19 +704,17 @@ FeedWriter.prototype = {
 
   /**
    * Returns the original URI object of the feed and ensures that this
    * component is only ever invoked from the preview document.
    * @param aWindow
    *        The window of the document invoking the BrowserFeedWriter
    */
   _getOriginalURI(aWindow) {
-    let docShell = aWindow.QueryInterface(Ci.nsIInterfaceRequestor)
-                          .getInterface(Ci.nsIWebNavigation)
-                          .QueryInterface(Ci.nsIDocShell);
+    let docShell = aWindow.docShell;
     let chan = docShell.currentDocumentChannel;
 
     // We probably need to call Inherit() for this, but right now we can't call
     // it from JS.
     let attrs = docShell.getOriginAttributes();
     let ssm = Services.scriptSecurityManager;
     let nullPrincipal = ssm.createNullPrincipal(attrs);
 

--- a/browser/components/feeds/WebContentConverter.js
+++ b/browser/components/feeds/WebContentConverter.js
@@ -318,19 +318,17 @@ WebContentConverterRegistrar.prototype =
 
 function WebContentConverterRegistrarContent() {
 }
 
 WebContentConverterRegistrarContent.prototype = {
   registerProtocolHandler(aProtocol, aURIString, aTitle, aBrowserOrWindow) {
     aProtocol = (aProtocol || "").toLowerCase();
     // aBrowserOrWindow must be a window.
-    let messageManager = aBrowserOrWindow.QueryInterface(Ci.nsIInterfaceRequestor)
-                                         .getInterface(Ci.nsIWebNavigation)
-                                         .QueryInterface(Ci.nsIDocShell)
+    let messageManager = aBrowserOrWindow.docShell
                                          .QueryInterface(Ci.nsIInterfaceRequestor)
                                          .getInterface(Ci.nsITabChild)
                                          .messageManager;
 
     let uri = Utils.checkAndGetURI(aURIString, aBrowserOrWindow);
     Utils.checkProtocolHandlerAllowed(aProtocol, aURIString, aBrowserOrWindow);
 
     messageManager.sendAsyncMessage("WCCR:registerProtocolHandler",

--- a/browser/components/nsBrowserContentHandler.js
+++ b/browser/components/nsBrowserContentHandler.js
@@ -205,18 +205,17 @@ function openBrowserWindow(cmdLine, urlO
   if (cmdLine.state == Ci.nsICommandLine.STATE_INITIAL_LAUNCH) {
     let win = Services.wm.getMostRecentWindow("navigator:blank");
     if (win) {
       // Remove the windowtype of our blank window so that we don't close it
       // later on when seeing cmdLine.preventDefault is true.
       win.document.documentElement.removeAttribute("windowtype");
 
       if (forcePrivate) {
-        win.QueryInterface(Ci.nsIInterfaceRequestor)
-           .getInterface(Ci.nsIWebNavigation)
+        win.docShell
            .QueryInterface(Ci.nsILoadContext)
            .usePrivateBrowsing = true;
       }
 
       win.location = chromeURL;
       win.arguments = args; // <-- needs to be a plain JS array here.
 
       return;
@@ -415,18 +414,17 @@ nsBrowserContentHandler.prototype = {
 
     // The global PB Service consumes this flag, so only eat it in per-window
     // PB builds.
     if (cmdLine.handleFlag("private", false) && PrivateBrowsingUtils.enabled) {
       PrivateBrowsingUtils.enterTemporaryAutoStartMode();
       if (cmdLine.state == Ci.nsICommandLine.STATE_INITIAL_LAUNCH) {
         let win = Services.wm.getMostRecentWindow("navigator:blank");
         if (win) {
-          win.QueryInterface(Ci.nsIInterfaceRequestor)
-             .getInterface(Ci.nsIWebNavigation)
+          win.docShell
              .QueryInterface(Ci.nsILoadContext)
              .usePrivateBrowsing = true;
         }
       }
     }
     if (cmdLine.handleFlag("setDefaultBrowser", false)) {
       ShellService.setDefaultBrowser(true, true);
     }

--- a/browser/components/preferences/in-content/findInPage.js
+++ b/browser/components/preferences/in-content/findInPage.js
@@ -180,19 +180,17 @@ var gSearchResultsPane = {
   /**
    * Get the selection instance from given window
    *
    * @param Object win
    *   The window object points to frame's window
    */
   getFindSelection(win) {
     // Yuck. See bug 138068.
-    let docShell = win.QueryInterface(Ci.nsIInterfaceRequestor)
-                      .getInterface(Ci.nsIWebNavigation)
-                      .QueryInterface(Ci.nsIDocShell);
+    let docShell = win.docShell;
 
     let controller = docShell.QueryInterface(Ci.nsIInterfaceRequestor)
                               .getInterface(Ci.nsISelectionDisplay)
                               .QueryInterface(Ci.nsISelectionController);
 
     let selection = controller.getSelection(Ci.nsISelectionController.SELECTION_FIND);
     selection.setColors("currentColor", "#ffe900", "currentColor", "#003eaa");
 

--- a/browser/components/preferences/in-content/subdialogs.js
+++ b/browser/components/preferences/in-content/subdialogs.js
@@ -517,20 +517,17 @@ SubDialog.prototype = {
 
   _untrapFocus() {
     this._frame.contentDocument.removeEventListener("keydown", this, true);
     this._closeButton.removeEventListener("keydown", this);
     window.removeEventListener("focus", this);
   },
 
   _getBrowser() {
-    return window.QueryInterface(Ci.nsIInterfaceRequestor)
-                 .getInterface(Ci.nsIWebNavigation)
-                 .QueryInterface(Ci.nsIDocShell)
-                 .chromeEventHandler;
+    return window.docShell.chromeEventHandler;
   },
 };
 
 var gSubDialog = {
   /**
    * New dialogs are stacked on top of the existing ones, and they are pushed
    * to the end of the _dialogs array.
    * @type {Array}

--- a/browser/components/preferences/in-content/sync.js
+++ b/browser/components/preferences/in-content/sync.js
@@ -351,20 +351,17 @@ var gSyncPane = {
       return;
     }
     win.switchToTabHavingURI(url, true, options);
   },
 
   // Replace the current tab with the specified URL.
   replaceTabWithUrl(url) {
     // Get the <browser> element hosting us.
-    let browser = window.QueryInterface(Ci.nsIInterfaceRequestor)
-      .getInterface(Ci.nsIWebNavigation)
-      .QueryInterface(Ci.nsIDocShell)
-      .chromeEventHandler;
+    let browser = window.docShell.chromeEventHandler;
     // And tell it to load our URL.
     browser.loadURI(url);
   },
 
   async signIn() {
     const url = await FxAccounts.config.promiseSignInURI(this._getEntryPoint());
     this.replaceTabWithUrl(url);
   },

--- a/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_context_and_chromeFlags.js
+++ b/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_context_and_chromeFlags.js
@@ -7,20 +7,18 @@
  * both the window's nsILoadContext, as well as on the initial
  * browser's content docShell nsILoadContext.
  *
  * @param win (nsIDOMWindow)
  *        An nsIDOMWindow in the parent process.
  * @return Promise
  */
 function assertWindowIsPrivate(win) {
-  let winDocShell = win.QueryInterface(Ci.nsIInterfaceRequestor)
-                       .getInterface(Ci.nsIDocShell);
-  let chromeFlags = winDocShell.QueryInterface(Ci.nsIDocShellTreeItem)
-                               .treeOwner
+  let winDocShell = win.docShell;
+  let chromeFlags = winDocShell.treeOwner
                                .QueryInterface(Ci.nsIInterfaceRequestor)
                                .getInterface(Ci.nsIXULWindow)
                                .chromeFlags;
 
   if (!win.gBrowser.selectedBrowser.hasContentOpener) {
     Assert.ok(chromeFlags & Ci.nsIWebBrowserChrome.CHROME_PRIVATE_WINDOW,
               "Should have the private window chrome flag");
   }

--- a/browser/components/sessionstore/SessionStorage.jsm
+++ b/browser/components/sessionstore/SessionStorage.jsm
@@ -68,19 +68,17 @@ var SessionStorageInternal = {
    *        A tab's global, i.e. the root frame we want to collect for.
    * @return Returns a nested object that will have hosts as keys and per-origin
    *         session storage data as strings. For example:
    *         {"https://example.com^userContextId=1": {"key": "value", "my_number": "123"}}
    */
   collect(content) {
     let data = {};
     let visitedOrigins = new Set();
-    let docShell = content.QueryInterface(Ci.nsIInterfaceRequestor)
-                          .getInterface(Ci.nsIWebNavigation)
-                          .QueryInterface(Ci.nsIDocShell);
+    let docShell = content.docShell;
 
     forEachNonDynamicChildFrame(content, frame => {
       let principal = getPrincipalForFrame(docShell, frame);
       if (!principal) {
         return;
       }
 
       // Get the origin of the current history entry

--- a/browser/components/sessionstore/SessionStore.jsm
+++ b/browser/components/sessionstore/SessionStore.jsm
@@ -1685,21 +1685,17 @@ var SessionStoreInternal = {
     // the user can't start changing any window state while we're waiting
     // for the flushes to finish.
     for (let window of this._browserWindows) {
       windowPromises.set(window, TabStateFlusher.flushWindow(window));
 
       // We have to wait for these messages to come up from
       // each window and each browser. In the meantime, hide
       // the windows to improve perceived shutdown speed.
-      let baseWin = window.QueryInterface(Ci.nsIInterfaceRequestor)
-                          .getInterface(Ci.nsIDocShell)
-                          .QueryInterface(Ci.nsIDocShellTreeItem)
-                          .treeOwner
-                          .QueryInterface(Ci.nsIBaseWindow);
+      let baseWin = window.docShell.treeOwner.QueryInterface(Ci.nsIBaseWindow);
       baseWin.visibility = false;
     }
 
     progress.total = windowPromises.size;
     progress.current = 0;
 
     // We'll iterate through the Promise array, yielding each one, so as to
     // provide useful progress information to AsyncShutdown.
@@ -4468,17 +4464,17 @@ var SessionStoreInternal = {
       let docElem = aWindow.document.documentElement;
       let attr = parseInt(docElem.getAttribute(aAttribute), 10);
       if (attr) {
         if (aAttribute != "width" && aAttribute != "height") {
           return attr;
         }
         // Width and height attribute report the inner size, but we want
         // to store the outer size, so add the difference.
-        let xulWin = aWindow.getInterface(Ci.nsIDocShell)
+        let xulWin = aWindow.docShell
                             .treeOwner
                             .QueryInterface(Ci.nsIInterfaceRequestor)
                             .getInterface(Ci.nsIXULWindow);
         let diff = aAttribute == "width"
           ? xulWin.outerToInnerWidthDifferenceInCSSPixels
           : xulWin.outerToInnerHeightDifferenceInCSSPixels;
         return attr + diff;
       }

--- a/browser/components/sessionstore/test/browser_docshell_uuid_consistency.js
+++ b/browser/components/sessionstore/test/browser_docshell_uuid_consistency.js
@@ -1,47 +1,44 @@
 // First test - open a tab and duplicate it, using session restore to restore the history into the new tab.
 add_task(async function duplicateTab() {
   const TEST_URL = "data:text/html,foo";
   let tab = BrowserTestUtils.addTab(gBrowser, TEST_URL);
   await BrowserTestUtils.browserLoaded(tab.linkedBrowser);
 
   await ContentTask.spawn(tab.linkedBrowser, null, function() {
-    let docshell = content.window.QueryInterface(Ci.nsIInterfaceRequestor)
-                                 .getInterface(Ci.nsIWebNavigation)
-                                 .QueryInterface(Ci.nsIDocShell);
+    let docshell = content.window.docShell
+                                 .QueryInterface(Ci.nsIWebNavigation);
     let shEntry = docshell.sessionHistory.legacySHistory.getEntryAtIndex(0, false);
     is(shEntry.docshellID.toString(), docshell.historyID.toString());
   });
 
   let tab2 = gBrowser.duplicateTab(tab);
   await BrowserTestUtils.browserLoaded(tab2.linkedBrowser);
 
   await ContentTask.spawn(tab2.linkedBrowser, null, function() {
-    let docshell = content.window.QueryInterface(Ci.nsIInterfaceRequestor)
-                                 .getInterface(Ci.nsIWebNavigation)
-                                 .QueryInterface(Ci.nsIDocShell);
+    let docshell = content.window.docShell
+                                 .QueryInterface(Ci.nsIWebNavigation);
     let shEntry = docshell.sessionHistory.legacySHistory.getEntryAtIndex(0, false);
     is(shEntry.docshellID.toString(), docshell.historyID.toString());
   });
 
   BrowserTestUtils.removeTab(tab);
   BrowserTestUtils.removeTab(tab2);
 });
 
 // Second test - open a tab and navigate across processes, which triggers sessionrestore to persist history.
 add_task(async function contentToChromeNavigate() {
   const TEST_URL = "data:text/html,foo";
   let tab = BrowserTestUtils.addTab(gBrowser, TEST_URL);
   await BrowserTestUtils.browserLoaded(tab.linkedBrowser);
 
   await ContentTask.spawn(tab.linkedBrowser, null, function() {
-    let docshell = content.window.QueryInterface(Ci.nsIInterfaceRequestor)
-                                 .getInterface(Ci.nsIWebNavigation)
-                                 .QueryInterface(Ci.nsIDocShell);
+    let docshell = content.window.docShell
+                                 .QueryInterface(Ci.nsIWebNavigation);
     let sh = docshell.sessionHistory;
     is(sh.count, 1);
     is(sh.legacySHistory.getEntryAtIndex(0, false).docshellID.toString(), docshell.historyID.toString());
   });
 
   // Force the browser to navigate to the chrome process.
   await ContentTask.spawn(tab.linkedBrowser, null, function() {
     const CHROME_URL = "about:config";

--- a/browser/extensions/formautofill/FormAutofillContent.jsm
+++ b/browser/extensions/formautofill/FormAutofillContent.jsm
@@ -261,18 +261,17 @@ let ProfileAutocomplete = {
         }
         this._fillFromAutocompleteRow(FormAutofillContent.activeInput);
         break;
       }
     }
   },
 
   _frameMMFromWindow(contentWindow) {
-    return contentWindow.QueryInterface(Ci.nsIInterfaceRequestor)
-                        .getInterface(Ci.nsIDocShell)
+    return contentWindow.docShell
                         .QueryInterface(Ci.nsIInterfaceRequestor)
                         .getInterface(Ci.nsIContentFrameMessageManager);
   },
 
   _getSelectedIndex(contentWindow) {
     let mm = this._frameMMFromWindow(contentWindow);
     let selectedIndexResult = mm.sendSyncMessage("FormAutoComplete:GetSelectedIndex", {});
     if (selectedIndexResult.length != 1 || !Number.isInteger(selectedIndexResult[0])) {
@@ -626,19 +625,17 @@ var FormAutofillContent = {
     if (!field || ChromeUtils.getClassName(field) !== "HTMLInputElement") {
       return;
     }
 
     formFillController.markAsAutofillField(field);
   },
 
   _messageManagerFromWindow(win) {
-    return win.QueryInterface(Ci.nsIInterfaceRequestor)
-              .getInterface(Ci.nsIWebNavigation)
-              .QueryInterface(Ci.nsIDocShell)
+    return win.docShell
               .QueryInterface(Ci.nsIInterfaceRequestor)
               .getInterface(Ci.nsIContentFrameMessageManager);
   },
 
   _onKeyDown(e) {
     delete FormAutofillContent._keyDownEnterForInput;
     let lastAutoCompleteResult = ProfileAutocomplete.lastProfileAutoCompleteResult;
     let focusedInput = FormAutofillContent.activeInput;

--- a/browser/extensions/formautofill/content/FormAutofillFrameScript.js
+++ b/browser/extensions/formautofill/content/FormAutofillFrameScript.js
@@ -83,17 +83,17 @@ var FormAutofillFrameScript = {
   },
 
   receiveMessage(message) {
     if (!FormAutofill.isAutofillEnabled) {
       return;
     }
 
     const doc = content.document;
-    const {chromeEventHandler} = doc.ownerGlobal.getInterface(Ci.nsIDocShell);
+    const {chromeEventHandler} = doc.ownerGlobal.docShell;
 
     switch (message.name) {
       case "FormAutofill:PreviewProfile": {
         FormAutofillContent.previewProfile(doc);
         break;
       }
       case "FormAutofill:ClearForm": {
         FormAutofillContent.clearForm();

--- a/browser/extensions/mortar/host/pdf/ppapi-content-sandbox.js
+++ b/browser/extensions/mortar/host/pdf/ppapi-content-sandbox.js
@@ -256,19 +256,17 @@ mm.addMessageListener("ppapipdf.js:save"
     if ("nsIPrivateBrowsingChannel" in Ci &&
         channel instanceof Ci.nsIPrivateBrowsingChannel) {
       channel.setPrivate(docIsPrivate);
     }
 
     let listener = {
       extListener: null,
       onStartRequest(aRequest, aContext) {
-        var loadContext = containerWindow
-                            .QueryInterface(Ci.nsIInterfaceRequestor)
-                            .getInterface(Ci.nsIWebNavigation)
+        var loadContext = containerWindow.docShell
                             .QueryInterface(Ci.nsILoadContext);
         this.extListener = extHelperAppSvc.doContent(
           "application/pdf", aRequest, loadContext, false);
         this.extListener.onStartRequest(aRequest, aContext);
       },
       onStopRequest(aRequest, aContext, aStatusCode) {
         if (this.extListener) {
           this.extListener.onStopRequest(aRequest, aContext, aStatusCode);

--- a/browser/extensions/pdfjs/content/PdfStreamConverter.jsm
+++ b/browser/extensions/pdfjs/content/PdfStreamConverter.jsm
@@ -263,19 +263,17 @@ class ChromeActions {
       if ("nsIPrivateBrowsingChannel" in Ci &&
           channel instanceof Ci.nsIPrivateBrowsingChannel) {
         channel.setPrivate(docIsPrivate);
       }
 
       var listener = {
         extListener: null,
         onStartRequest(aRequest, aContext) {
-          var loadContext = self.domWindow
-                                .QueryInterface(Ci.nsIInterfaceRequestor)
-                                .getInterface(Ci.nsIWebNavigation)
+          var loadContext = self.domWindow.docShell
                                 .QueryInterface(Ci.nsILoadContext);
           this.extListener = extHelperAppSvc.doContent(
             (data.isAttachment ? "application/octet-stream" :
                                  "application/pdf"),
             aRequest, loadContext, false);
           this.extListener.onStartRequest(aRequest, aContext);
         },
         onStopRequest(aRequest, aContext, aStatusCode) {
@@ -409,18 +407,17 @@ class ChromeActions {
     } else {
       message = getLocalizedString(strings, "unsupported_feature");
     }
     PdfJsTelemetry.onFallback();
     PdfjsContentUtils.displayWarning(domWindow, message,
       getLocalizedString(strings, "open_with_different_viewer"),
       getLocalizedString(strings, "open_with_different_viewer", "accessKey"));
 
-    let winmm = domWindow.QueryInterface(Ci.nsIInterfaceRequestor)
-                         .getInterface(Ci.nsIDocShell)
+    let winmm = domWindow.docShell
                          .QueryInterface(Ci.nsIInterfaceRequestor)
                          .getInterface(Ci.nsIContentFrameMessageManager);
 
     winmm.addMessageListener("PDFJS:Child:fallbackDownload",
       function fallbackDownload(msg) {
         let data = msg.data;
         sendResponse(data.download);
 
@@ -437,18 +434,17 @@ class ChromeActions {
     var result = data.result;
     var findPrevious = data.findPrevious;
     var findPreviousType = typeof findPrevious;
     if ((typeof result !== "number" || result < 0 || result > 3) ||
         (findPreviousType !== "undefined" && findPreviousType !== "boolean")) {
       return;
     }
 
-    var winmm = this.domWindow.QueryInterface(Ci.nsIInterfaceRequestor)
-                              .getInterface(Ci.nsIDocShell)
+    var winmm = this.domWindow.docShell
                               .QueryInterface(Ci.nsIInterfaceRequestor)
                               .getInterface(Ci.nsIContentFrameMessageManager);
 
     winmm.sendAsyncMessage("PDFJS:Parent:updateControlState", data);
   }
 
   setPreferences(prefs, sendResponse) {
     var defaultBranch = Services.prefs.getDefaultBranch(PREF_PREFIX + ".");
@@ -754,18 +750,17 @@ class RequestListener {
 
 /**
  * Forwards events from the eventElement to the contentWindow only if the
  * content window matches the currently selected browser window.
  */
 class FindEventManager {
   constructor(contentWindow) {
     this.contentWindow = contentWindow;
-    this.winmm = contentWindow.QueryInterface(Ci.nsIInterfaceRequestor)
-                              .getInterface(Ci.nsIDocShell)
+    this.winmm = contentWindow.docShell
                               .QueryInterface(Ci.nsIInterfaceRequestor)
                               .getInterface(Ci.nsIContentFrameMessageManager);
   }
 
   bind() {
     var unload = (evt) => {
       this.unbind();
       this.contentWindow.removeEventListener(evt.type, unload);

--- a/browser/extensions/pdfjs/content/PdfjsContentUtils.jsm
+++ b/browser/extensions/pdfjs/content/PdfjsContentUtils.jsm
@@ -86,18 +86,17 @@ var PdfjsContentUtils = {
   },
 
   /*
    * Request the display of a notification warning in the associated window
    * when the renderer isn't sure a pdf displayed correctly.
    */
   displayWarning(aWindow, aMessage, aLabel, aAccessKey) {
     // the child's dom frame mm associated with the window.
-    let winmm = aWindow.QueryInterface(Ci.nsIInterfaceRequestor)
-                       .getInterface(Ci.nsIDocShell)
+    let winmm = aWindow.docShell
                        .QueryInterface(Ci.nsIInterfaceRequestor)
                        .getInterface(Ci.nsIContentFrameMessageManager);
     winmm.sendAsyncMessage("PDFJS:Parent:displayWarning", {
       message: aMessage,
       label: aLabel,
       accessKey: aAccessKey,
     });
   },

--- a/browser/modules/BlockedSiteContent.jsm
+++ b/browser/modules/BlockedSiteContent.jsm
@@ -127,19 +127,17 @@ var BlockedSiteContent = {
     if (/e=malwareBlocked/.test(ownerDoc.documentURI)) {
       reason = "malware";
     } else if (/e=unwantedBlocked/.test(ownerDoc.documentURI)) {
       reason = "unwanted";
     } else if (/e=harmfulBlocked/.test(ownerDoc.documentURI)) {
       reason = "harmful";
     }
 
-    let docShell = ownerDoc.defaultView.QueryInterface(Ci.nsIInterfaceRequestor)
-                                       .getInterface(Ci.nsIWebNavigation)
-                                      .QueryInterface(Ci.nsIDocShell);
+    let docShell = ownerDoc.defaultView.docShell;
 
     global.sendAsyncMessage("Browser:SiteBlockedError", {
       location: ownerDoc.location.href,
       reason,
       elementId: targetElement.getAttribute("id"),
       isTopFrame: (ownerDoc.defaultView.parent === ownerDoc.defaultView),
       blockedInfo: getSiteBlockedErrorDetails(docShell),
     });

--- a/browser/modules/ContentObservers.js
+++ b/browser/modules/ContentObservers.js
@@ -32,18 +32,17 @@ var gDecoderDoctorObserver = function(su
   let win = subject.top;
   let mm = getMessageManagerForWindow(win);
   if (mm) {
     mm.sendAsyncMessage("DecoderDoctor:Notification", data);
   }
 };
 
 function getMessageManagerForWindow(aContentWindow) {
-  let ir = aContentWindow.QueryInterface(Ci.nsIInterfaceRequestor)
-                         .getInterface(Ci.nsIDocShell)
+  let ir = aContentWindow.docShell
                          .sameTypeRootTreeItem
                          .QueryInterface(Ci.nsIInterfaceRequestor);
   try {
     // If e10s is disabled, this throws NS_NOINTERFACE for closed tabs.
     return ir.getInterface(Ci.nsIContentFrameMessageManager);
   } catch (e) {
     if (e.result == Cr.NS_NOINTERFACE) {
       return null;

--- a/browser/modules/ContentWebRTC.jsm
+++ b/browser/modules/ContentWebRTC.jsm
@@ -414,27 +414,20 @@ function getTabStateForContentWindow(aCo
   return tabState;
 }
 
 function getInnerWindowIDForWindow(aContentWindow) {
   return aContentWindow.windowUtils.currentInnerWindowID;
 }
 
 function getMessageManagerForWindow(aContentWindow) {
-  aContentWindow.QueryInterface(Ci.nsIInterfaceRequestor);
-
-  let docShell;
-  try {
-    // This throws NS_NOINTERFACE for closed tabs.
-    docShell = aContentWindow.getInterface(Ci.nsIDocShell);
-  } catch (e) {
-    if (e.result == Cr.NS_NOINTERFACE) {
-      return null;
-    }
-    throw e;
+  let docShell = aContentWindow.docShell;
+  if (!docShell) {
+    // Closed tab.
+    return null;
   }
 
   let ir = docShell.sameTypeRootTreeItem
                    .QueryInterface(Ci.nsIInterfaceRequestor);
   try {
     // This throws NS_NOINTERFACE for closed tabs (only with e10s enabled).
     return ir.getInterface(Ci.nsIContentFrameMessageManager);
   } catch (e) {

--- a/browser/modules/FormSubmitObserver.jsm
+++ b/browser/modules/FormSubmitObserver.jsm
@@ -31,20 +31,18 @@ FormSubmitObserver.prototype =
   /*
    * Public apis
    */
 
   init(aWindow, aTabChildGlobal) {
     this._content = aWindow;
     this._tab = aTabChildGlobal;
     this._mm =
-      this._content.QueryInterface(Ci.nsIInterfaceRequestor)
-                   .getInterface(Ci.nsIDocShell)
+      this._content.docShell
                    .sameTypeRootTreeItem
-                   .QueryInterface(Ci.nsIDocShell)
                    .QueryInterface(Ci.nsIInterfaceRequestor)
                    .getInterface(Ci.nsIContentFrameMessageManager);
 
     this._tab.addEventListener("pageshow", this);
     this._tab.addEventListener("unload", this);
   },
 
   uninit() {

--- a/browser/modules/LightWeightThemeWebInstallListener.jsm
+++ b/browser/modules/LightWeightThemeWebInstallListener.jsm
@@ -46,14 +46,13 @@ var LightWeightThemeWebInstallListener =
 
   _resetPreviewWindow() {
     this._previewWindow.removeEventListener("pagehide", this, true);
     this._previewWindow = null;
   }
 };
 
 function getMessageManagerForContent(content) {
-  return content.QueryInterface(Ci.nsIInterfaceRequestor)
-                .getInterface(Ci.nsIDocShell)
+  return content.docShell
                 .sameTypeRootTreeItem
                 .QueryInterface(Ci.nsIInterfaceRequestor)
                 .getInterface(Ci.nsIContentFrameMessageManager);
 }

--- a/browser/modules/LightweightThemeChildHelper.jsm
+++ b/browser/modules/LightweightThemeChildHelper.jsm
@@ -36,18 +36,17 @@ var LightweightThemeChildHelper = {
   /**
    * Update the theme data for the whole process
    * @param {Array} changedKeys The sharedData keys that were changed.
    */
   _updateProcess(changedKeys) {
     const windowEnumerator = Services.ww.getWindowEnumerator();
     while (windowEnumerator.hasMoreElements()) {
       const window = windowEnumerator.getNext().QueryInterface(Ci.nsIDOMWindow);
-      const tabChildGlobal = window.QueryInterface(Ci.nsIInterfaceRequestor)
-                                   .getInterface(Ci.nsIDocShell)
+      const tabChildGlobal = window.docShell
                                    .sameTypeRootTreeItem
                                    .QueryInterface(Ci.nsIInterfaceRequestor)
                                    .getInterface(Ci.nsIContentFrameMessageManager);
       const {chromeOuterWindowID, content} = tabChildGlobal;
       if (changedKeys.includes(`theme/${chromeOuterWindowID}`) &&
           content && this.whitelist.has(content.document.documentURI)) {
         this.update(chromeOuterWindowID, content);
       }

--- a/browser/modules/PermissionUI.jsm
+++ b/browser/modules/PermissionUI.jsm
@@ -403,22 +403,17 @@ var PermissionPromptForRequestPrototype 
 
   get browser() {
     // In the e10s-case, the <xul:browser> will be at request.element.
     // In the single-process case, we have to use some XPCOM incantations
     // to resolve to the <xul:browser>.
     if (this.request.element) {
       return this.request.element;
     }
-    return this.request
-               .window
-               .QueryInterface(Ci.nsIInterfaceRequestor)
-               .getInterface(Ci.nsIWebNavigation)
-               .QueryInterface(Ci.nsIDocShell)
-               .chromeEventHandler;
+    return this.request.window.docShell.chromeEventHandler;
   },
 
   get principal() {
     return this.request.principal;
   },
 
   cancel() {
     this.request.cancel();

--- a/browser/modules/WindowsPreviewPerTab.jsm
+++ b/browser/modules/WindowsPreviewPerTab.jsm
@@ -424,20 +424,17 @@ TabWindow.prototype = {
     this.previews.set(tab, controller.preview);
     AeroPeek.addPreview(controller.preview);
     // updateTitleAndTooltip relies on having controller.preview which is lazily resolved.
     // Now that we've updated this.previews, it will resolve successfully.
     controller.updateTitleAndTooltip();
   },
 
   createTabPreview(controller) {
-    let docShell = this.win
-                  .QueryInterface(Ci.nsIInterfaceRequestor)
-                  .getInterface(Ci.nsIWebNavigation)
-                  .QueryInterface(Ci.nsIDocShell);
+    let docShell = this.win.docShell;
     let preview = AeroPeek.taskbar.createTaskbarTabPreview(docShell, controller);
     preview.visible = AeroPeek.enabled;
     preview.active = this.tabbrowser.selectedTab == controller.tab;
     this.onLinkIconAvailable(controller.tab.linkedBrowser,
                              controller.tab.getAttribute("image"));
     return preview;
   },
 

--- a/browser/tools/mozscreenshots/browser_boundingbox.js
+++ b/browser/tools/mozscreenshots/browser_boundingbox.js
@@ -1,17 +1,17 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/
  */
 
 "use strict";
 
 add_task(async function() {
-  const scale = window.QueryInterface(Ci.nsIInterfaceRequestor)
-                      .getInterface(Ci.nsIDocShell).QueryInterface(Ci.nsIBaseWindow)
+  const scale = window.docShell
+                      .QueryInterface(Ci.nsIBaseWindow)
                       .devicePixelsPerDesktopPixel;
   let {bounds, rects} = TestRunner._findBoundingBox(["#tabbrowser-tabs"]);
   let element = document.querySelector("#tabbrowser-tabs");
   let tabBar = element.ownerDocument.getBoxObjectFor(element);
 
   // Calculate expected values
   let expectedLeft = scale * (tabBar.screenX - TestRunner.croppingPadding);
   let expectedTop = scale * (tabBar.screenY - TestRunner.croppingPadding);