--- a/.taskcluster.yml
+++ b/.taskcluster.yml
@@ -31,17 +31,17 @@ scopes:
 # - as_slugid:      convert a label into a slugId
 # - from_now:       generate a timestamp at a fixed offset from now
 
 tasks:
   - taskId: '{{#as_slugid}}decision task{{/as_slugid}}'
     task:
       created: '{{now}}'
       deadline: '{{#from_now}}1 day{{/from_now}}'
-      expires: '{{#from_now}}14 day{{/from_now}}'
+      expires: '{{#from_now}}365 day{{/from_now}}'
       metadata:
         owner: mozilla-taskcluster-maintenance@mozilla.com
         source: {{{source}}}
         name: "Gecko Decision Task"
         description: |
             The task that creates all of the other tasks in the task graph
 
       workerType: "gecko-decision"
@@ -65,48 +65,58 @@ tasks:
       payload:
         env:
           # checkout-gecko uses these to check out the source; the inputs
           # to `mach taskgraph decision` are all on the command line.
           GECKO_BASE_REPOSITORY: 'https://hg.mozilla.org/mozilla-unified'
           GECKO_HEAD_REPOSITORY: '{{{url}}}'
           GECKO_HEAD_REF: '{{revision}}'
           GECKO_HEAD_REV: '{{revision}}'
-          # Arguments passed into `mach taskgraph decision`
-          # TODO use mozilla-unified for the base repository once the tc-vcs
-          # tar.gz archives are created or tc-vcs isn't being used.
-          DECISION_ARGS: >
-            --pushlog-id='{{pushlog_id}}'
-            --project='{{project}}'
-            --message='{{comment}}'
-            --owner='{{owner}}'
-            --level='{{level}}'
-            --base-repository='https://hg.mozilla.org/mozilla-central'
-            --head-repository='{{{url}}}'
-            --head-ref='{{revision}}'
-            --head-rev='{{revision}}'
-            --revision-hash='{{revision_hash}}'
 
         cache:
           level-{{level}}-hg-shared: /home/worker/hg-shared
-          level-{{level}}-gecko-decision: /home/worker/workspace
+          level-{{level}}-checkouts: /home/worker/checkouts
 
         features:
           taskclusterProxy: true
 
         # Note: This task is built server side without the context or tooling that
         # exist in tree so we must hard code the version
-        image: 'taskcluster/decision:0.1.2'
+        image: 'taskcluster/decision:0.1.3'
 
         maxRunTime: 1800
 
+        # TODO use mozilla-unified for the base repository once the tc-vcs
+        # tar.gz archives are created or tc-vcs isn't being used.
         command:
-          - /home/worker/bin/run-decision
+          - /home/worker/bin/run-task
+          - '--vcs-checkout=/home/worker/checkouts/gecko'
+          - '--'
+          - bash
+          - -cx
+          - >
+              cd /home/worker/checkouts/gecko &&
+              ln -s /home/worker/artifacts artifacts &&
+              ./mach --log-no-times taskgraph decision
+              --pushlog-id='{{pushlog_id}}'
+              --project='{{project}}'
+              --message='{{comment}}'
+              --owner='{{owner}}'
+              --level='{{level}}'
+              --base-repository='https://hg.mozilla.org/mozilla-central'
+              --head-repository='{{{url}}}'
+              --head-ref='{{revision}}'
+              --head-rev='{{revision}}'
+              --revision-hash='{{revision_hash}}'
 
         artifacts:
           'public':
             type: 'directory'
             path: '/home/worker/artifacts'
+            expires: '{{#from_now}}364 days{{/from_now}}'
+          'public/docker_image_contexts':
+            type: 'directory'
+            path: '/home/worker/docker_image_contexts'
             expires: '{{#from_now}}7 days{{/from_now}}'
 
       extra:
         treeherder:
           symbol: D

--- a/browser/base/content/test/general/browser_addKeywordSearch.js
+++ b/browser/base/content/test/general/browser_addKeywordSearch.js
@@ -5,29 +5,29 @@ var testData = [
   /* baseURI, field name, expected */
   [ 'http://example.com/', 'q', 'http://example.com/?q=%s' ],
   [ 'http://example.com/new-path-here/', 'q', 'http://example.com/new-path-here/?q=%s' ],
   [ '', 'q', 'http://example.org/browser/browser/base/content/test/general/dummy_page.html?q=%s' ],
   // Tests for proper behaviour when called on a form whose action contains a question mark.
   [ 'http://example.com/search?oe=utf-8', 'q', 'http://example.com/search?oe=utf-8&q=%s' ],
 ];
 
-var mm = gBrowser.selectedBrowser.messageManager;
-
 add_task(function*() {
   yield BrowserTestUtils.withNewTab({
     gBrowser,
     url: "http://example.org/browser/browser/base/content/test/general/dummy_page.html",
   }, function* (browser) {
     yield ContentTask.spawn(browser, null, function* () {
       let doc = content.document;
       let base = doc.createElement("base");
       doc.head.appendChild(base);
     });
 
+    var mm = browser.messageManager;
+
     for (let [baseURI, fieldName, expected] of testData) {
       let popupShownPromise = BrowserTestUtils.waitForEvent(document.getElementById("contentAreaContextMenu"),
                                                             "popupshown");
 
       yield ContentTask.spawn(browser, { baseURI, fieldName }, function* (args) {
         let doc = content.document;
 
         let base = doc.querySelector('head > base');

--- a/browser/base/content/test/general/browser_tabfocus.js
+++ b/browser/base/content/test/general/browser_tabfocus.js
@@ -3,24 +3,42 @@
  */
 
 var testPage1 = "<html id='html1'><body id='body1'><button id='button1'>Tab 1</button></body></html>";
 var testPage2 = "<html id='html2'><body id='body2'><button id='button2'>Tab 2</button></body></html>";
 var testPage3 = "<html id='html3'><body id='body3'><button id='button3'>Tab 3</button></body></html>";
 
 const fm = Services.focus;
 
+function EventStore() {
+  this["main-window"] = [];
+  this["window1"] = [];
+  this["window2"] = [];
+};
+
+EventStore.prototype = {
+  "push": function (event) {
+    if (event.indexOf("1") > -1) {
+      this["window1"].push(event);
+    } else if (event.indexOf("2") > -1) {
+      this["window2"].push(event);
+    } else {
+      this["main-window"].push(event);
+    }
+  }
+}
+
 var tab1 = null;
 var tab2 = null;
 var browser1 = null;
 var browser2 = null;
-var _browser_tabfocus_test_lastfocus;
-var _browser_tabfocus_test_lastfocuswindow = null;
-var actualEvents = [];
-var expectedEvents = [];
+var _lastfocus;
+var _lastfocuswindow = null;
+var actualEvents = new EventStore();
+var expectedEvents = new EventStore();
 var currentTestName = "";
 var _expectedElement = null;
 var _expectedWindow = null;
 
 var currentPromiseResolver = null;
 
 function* getFocusedElementForBrowser(browser, dontCheckExtraFocus = false)
 {
@@ -133,18 +151,18 @@ add_task(function*() {
   var messages = "";
   if (gMultiProcessBrowser) {
     messageManager.addMessageListener("Browser:FocusChanged", message => {
       actualEvents.push(message.data.details);
       compareFocusResults();
     });
   }
 
-  _browser_tabfocus_test_lastfocus = "urlbar";
-  _browser_tabfocus_test_lastfocuswindow = "main-window";
+  _lastfocus = "urlbar";
+  _lastfocuswindow = "main-window";
 
   window.addEventListener("focus", _browser_tabfocus_test_eventOccured, true);
   window.addEventListener("blur", _browser_tabfocus_test_eventOccured, true);
 
   // make sure that the focus initially starts out blank
   var fm = Services.focus;
   var focusedWindow = {};
 
@@ -324,19 +342,19 @@ add_task(function*() {
     document.getElementById('Browser:Back').doCommand();
   });
 
   is(window.document.activeElement, gURLBar.inputField, "urlbar still focused after navigating back");
 
   // Document navigation with F6 does not yet work in mutli-process browsers.
   if (!gMultiProcessBrowser) {
     gURLBar.focus();
-    actualEvents = [];
-    _browser_tabfocus_test_lastfocus = "urlbar";
-    _browser_tabfocus_test_lastfocuswindow = "main-window";
+    actualEvents = new EventStore();
+    _lastfocus = "urlbar";
+    _lastfocuswindow = "main-window";
 
     yield expectFocusShift(() => EventUtils.synthesizeKey("VK_F6", { }),
                            "window1", "html1",
                            true, "switch document forward with f6");
 
     EventUtils.synthesizeKey("VK_F6", { });
     is(fm.focusedWindow, window, "switch document forward again with f6");
 
@@ -411,36 +429,29 @@ function getId(element)
   return (element.localName == "input") ? "urlbar" : element.id;
 }
 
 function compareFocusResults()
 {
   if (!currentPromiseResolver)
     return;
 
-  if (actualEvents.length < expectedEvents.length)
-    return;
+  let winIds = ["main-window", "window1", "window2"];
 
-  for (let e = 0; e < expectedEvents.length; e++) {
-    // When remote browsers are used, the child process events can occur before or after the
-    // browser focusing. Allow either order.
-    if (gMultiProcessBrowser && actualEvents[e] != expectedEvents[e] &&
-        actualEvents[e].startsWith("focus: browser")) {
+  for (let winId of winIds) {
+    if (actualEvents[winId].length < expectedEvents[winId].length)
+      return;
+  }
 
-      // Ensure that this event is expected later, and remove the later expected event and
-      // reinsert it at the current index.
-      let foundLaterIndex = expectedEvents.indexOf(actualEvents[e], e + 1);
-      if (foundLaterIndex > e) {
-        expectedEvents.splice(e, 0, expectedEvents.splice(foundLaterIndex, 1)[0]);
-      }
+  for (let winId of winIds) {
+    for (let e = 0; e < expectedEvents.length; e++) {
+      is(actualEvents[winId][e], expectedEvents[winId][e], currentTestName + " events [event " + e + "]");
     }
-
-    is(actualEvents[e], expectedEvents[e], currentTestName + " events [event " + e + "]");
+    actualEvents[winId] = [];
   }
-  actualEvents = [];
 
   // Use executeSoon as this will be called during a focus/blur event handler
   executeSoon(() => {
     let matchWindow = window;
     if (gMultiProcessBrowser) {
       is(_expectedWindow, "main-window", "main-window is always expected");
     }
     else if (_expectedWindow != "main-window") {
@@ -475,17 +486,17 @@ function* expectFocusShiftAfterTabSwitch
   yield tabSwitchPromise;
 }
 
 function* expectFocusShift(callback, expectedWindow, expectedElement, focusChanged, testid)
 {
   currentPromiseResolver = null;
   currentTestName = testid;
 
-  expectedEvents = [];
+  expectedEvents = new EventStore();
 
   if (focusChanged) {
     _expectedElement = expectedElement;
     _expectedWindow = expectedWindow;
 
     // When the content is in a child process, the expected element in the chrome window
     // will always be the urlbar or a browser element.
     if (gMultiProcessBrowser) {
@@ -493,67 +504,67 @@ function* expectFocusShift(callback, exp
         _expectedElement = "browser1";
       }
       else if (_expectedWindow == "window2") {
         _expectedElement = "browser2";
       }
       _expectedWindow = "main-window";
     }
 
-    if (gMultiProcessBrowser && _browser_tabfocus_test_lastfocuswindow != "main-window" &&
-        _browser_tabfocus_test_lastfocuswindow != expectedWindow) {
-      let browserid = _browser_tabfocus_test_lastfocuswindow == "window1" ? "browser1" : "browser2";
+    if (gMultiProcessBrowser && _lastfocuswindow != "main-window" &&
+        _lastfocuswindow != expectedWindow) {
+      let browserid = _lastfocuswindow == "window1" ? "browser1" : "browser2";
       expectedEvents.push("blur: " + browserid);
     }
 
     var newElementIsFocused = (expectedElement && !expectedElement.startsWith("html"));
     if (newElementIsFocused && gMultiProcessBrowser &&
-        _browser_tabfocus_test_lastfocuswindow != "main-window" &&
+        _lastfocuswindow != "main-window" &&
         expectedWindow == "main-window") {
       // When switching from a child to a chrome element, the focus on the element will arrive first.
       expectedEvents.push("focus: " + expectedElement);
       newElementIsFocused = false;
     }
 
-    if (_browser_tabfocus_test_lastfocus && _browser_tabfocus_test_lastfocus != _expectedElement)
-      expectedEvents.push("blur: " + _browser_tabfocus_test_lastfocus);
+    if (_lastfocus && _lastfocus != _expectedElement)
+      expectedEvents.push("blur: " + _lastfocus);
 
-    if (_browser_tabfocus_test_lastfocuswindow &&
-        _browser_tabfocus_test_lastfocuswindow != expectedWindow) {
+    if (_lastfocuswindow &&
+        _lastfocuswindow != expectedWindow) {
 
-      if (!gMultiProcessBrowser || _browser_tabfocus_test_lastfocuswindow != "main-window") {
-        expectedEvents.push("blur: " + _browser_tabfocus_test_lastfocuswindow + "-document");
-        expectedEvents.push("blur: " + _browser_tabfocus_test_lastfocuswindow + "-window");
+      if (!gMultiProcessBrowser || _lastfocuswindow != "main-window") {
+        expectedEvents.push("blur: " + _lastfocuswindow + "-document");
+        expectedEvents.push("blur: " + _lastfocuswindow + "-window");
       }
     }
 
-    if (expectedWindow && _browser_tabfocus_test_lastfocuswindow != expectedWindow) {
+    if (expectedWindow && _lastfocuswindow != expectedWindow) {
       if (gMultiProcessBrowser && expectedWindow != "main-window") {
         let browserid = expectedWindow == "window1" ? "browser1" : "browser2";
         expectedEvents.push("focus: " + browserid);
       }
 
       if (!gMultiProcessBrowser || expectedWindow != "main-window") {
         expectedEvents.push("focus: " + expectedWindow + "-document");
         expectedEvents.push("focus: " + expectedWindow + "-window");
       }
     }
 
     if (newElementIsFocused) {
       expectedEvents.push("focus: " + expectedElement);
     }
 
-    _browser_tabfocus_test_lastfocus = expectedElement;
-    _browser_tabfocus_test_lastfocuswindow = expectedWindow;
+    _lastfocus = expectedElement;
+    _lastfocuswindow = expectedWindow;
   }
 
   return new Promise((resolve, reject) => {
     currentPromiseResolver = resolve;
     callback();
 
     // No events are expected, so resolve the promise immediately.
-    if (!expectedEvents.length) {
+    if (expectedEvents["main-window"].length + expectedEvents["window1"].length + expectedEvents["window2"].length == 0) {
       currentPromiseResolver();
       currentPromiseResolver = null;
     }
   });
 }
 

--- a/browser/components/extensions/test/browser/browser_ext_optionsPage_privileges.js
+++ b/browser/components/extensions/test/browser/browser_ext_optionsPage_privileges.js
@@ -25,17 +25,17 @@ add_task(function* test_tab_options_priv
       browser.runtime.sendMessage({msgName: "removeTabId", tabId: tab.id});
     }).catch(error => {
       browser.test.log(`Error: ${error} :: ${error.stack}`);
       browser.test.notifyFail("options-ui-privileges");
     });
   }
 
   let extension = ExtensionTestUtils.loadExtension({
-    useAddonManager: true,
+    useAddonManager: "temporary",
 
     manifest: {
       "permissions": ["tabs"],
       "options_ui": {
         "page": "options.html",
       },
     },
     files: {

--- a/browser/components/extensions/test/browser/browser_ext_runtime_openOptionsPage.js
+++ b/browser/components/extensions/test/browser/browser_ext_runtime_openOptionsPage.js
@@ -1,15 +1,15 @@
 /* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
 /* vim: set sts=2 sw=2 et tw=80: */
 "use strict";
 
 function* loadExtension(options) {
   let extension = ExtensionTestUtils.loadExtension({
-    useAddonManager: true,
+    useAddonManager: "temporary",
 
     manifest: Object.assign({
       "permissions": ["tabs"],
     }, options.manifest),
 
     files: {
       "options.html": `<!DOCTYPE html>
         <html>

--- a/browser/components/sessionstore/test/browser_crashedTabs.js
+++ b/browser/components/sessionstore/test/browser_crashedTabs.js
@@ -3,20 +3,24 @@
 
 "use strict";
 
 requestLongerTimeout(10);
 
 const PAGE_1 = "data:text/html,<html><body>A%20regular,%20everyday,%20normal%20page.";
 const PAGE_2 = "data:text/html,<html><body>Another%20regular,%20everyday,%20normal%20page.";
 
-// Turn off tab animations for testing
-Services.prefs.setBoolPref("browser.tabs.animate", false);
-registerCleanupFunction(() => {
-  Services.prefs.clearUserPref("browser.tabs.animate");
+// Turn off tab animations for testing and use a single content process
+// for these tests since we want to test tabs within the crashing process here.
+add_task(function* test_initialize() {
+  yield SpecialPowers.pushPrefEnv({
+    set: [
+      [ "dom.ipc.processCount", 1 ],
+      [ "browser.tabs.animate", false]
+  ] });
 });
 
 // Allow tabs to restore on demand so we can test pending states
 Services.prefs.clearUserPref("browser.sessionstore.restore_on_demand");
 
 function clickButton(browser, id) {
   info("Clicking " + id);
 

--- a/browser/config/mozconfigs/linux32/release
+++ b/browser/config/mozconfigs/linux32/release
@@ -1,14 +1,14 @@
 # This make file should be identical to the beta mozconfig, apart from the
 # safeguard below
 MOZ_AUTOMATION_SDK=${MOZ_AUTOMATION_SDK-1}
 
 if [ -n "$ENABLE_RELEASE_PROMOTION" ]; then
-  MOZ_AUTOMATION_UPLOAD_SYMBOLS=1
+  MOZ_AUTOMATION_UPLOAD_SYMBOLS=${MOZ_AUTOMATION_UPLOAD_SYMBOLS-1}
   MOZ_AUTOMATION_UPDATE_PACKAGING=1
 fi
 
 . "$topsrcdir/browser/config/mozconfigs/linux32/common-opt"
 
 ac_add_options --enable-official-branding
 ac_add_options --enable-verify-mar
 

--- a/browser/config/mozconfigs/linux64/release
+++ b/browser/config/mozconfigs/linux64/release
@@ -1,14 +1,14 @@
 # This make file should be identical to the beta mozconfig, apart from the
 # safeguard below
 MOZ_AUTOMATION_SDK=${MOZ_AUTOMATION_SDK-1}
 
 if [ -n "$ENABLE_RELEASE_PROMOTION" ]; then
-  MOZ_AUTOMATION_UPLOAD_SYMBOLS=1
+  MOZ_AUTOMATION_UPLOAD_SYMBOLS=${MOZ_AUTOMATION_UPLOAD_SYMBOLS-1}
   MOZ_AUTOMATION_UPDATE_PACKAGING=1
 fi
 
 . "$topsrcdir/browser/config/mozconfigs/linux64/common-opt"
 
 ac_add_options --enable-official-branding
 ac_add_options --enable-verify-mar
 

--- a/browser/config/tooltool-manifests/win32/releng.manifest
+++ b/browser/config/tooltool-manifests/win32/releng.manifest
@@ -25,15 +25,15 @@
 "size": 167175,
 "digest": "0b71a936edf5bd70cf274aaa5d7abc8f77fe8e7b5593a208f805cc9436fac646b9c4f0b43c2b10de63ff3da671497d35536077ecbc72dba7f8159a38b580f831",
 "algorithm": "sha512",
 "filename": "sccache.tar.bz2",
 "unpack": true
 },
 {
 "version": "Visual Studio 2015 Update 2 / SDK 10.0.10586.0/212",
-"size": 332343834,
-"digest": "55814aaabcd4aa51fe85918ec02a8c29bc067d41ee79ddcfd628daaba5a06d4241a73a51bf5a8bc69cc762b52551009f44b05e65682c45b4684c17fb2d017c2c",
+"size": 332442800,
+"digest": "995394a4a515c7cb0f8595f26f5395361a638870dd0bbfcc22193fe1d98a0c47126057d5999cc494f3f3eac5cb49160e79757c468f83ee5797298e286ef6252c",
 "algorithm": "sha512",
 "filename": "vs2015u2.zip",
 "unpack": true
 }
 ]

--- a/browser/config/tooltool-manifests/win64/releng.manifest
+++ b/browser/config/tooltool-manifests/win64/releng.manifest
@@ -26,15 +26,15 @@
 "size": 167175,
 "digest": "0b71a936edf5bd70cf274aaa5d7abc8f77fe8e7b5593a208f805cc9436fac646b9c4f0b43c2b10de63ff3da671497d35536077ecbc72dba7f8159a38b580f831",
 "algorithm": "sha512",
 "filename": "sccache.tar.bz2",
 "unpack": true
 },
 {
 "version": "Visual Studio 2015 Update 2 / SDK 10.0.10586.0/212",
-"size": 332343834,
-"digest": "55814aaabcd4aa51fe85918ec02a8c29bc067d41ee79ddcfd628daaba5a06d4241a73a51bf5a8bc69cc762b52551009f44b05e65682c45b4684c17fb2d017c2c",
+"size": 332442800,
+"digest": "995394a4a515c7cb0f8595f26f5395361a638870dd0bbfcc22193fe1d98a0c47126057d5999cc494f3f3eac5cb49160e79757c468f83ee5797298e286ef6252c",
 "algorithm": "sha512",
 "filename": "vs2015u2.zip",
 "unpack": true
 }
 ]

--- a/build/autoconf/compiler-opts.m4
+++ b/build/autoconf/compiler-opts.m4
@@ -20,17 +20,16 @@ dnl Default to MSVC for win32 and gcc-4.
 dnl ==============================================================
 if test -z "$CROSS_COMPILE"; then
 case "$target" in
 *-mingw*)
     if test -z "$CC"; then CC=cl; fi
     if test -z "$CXX"; then CXX=cl; fi
     if test -z "$CPP"; then CPP="$CC -E -nologo"; fi
     if test -z "$CXXCPP"; then CXXCPP="$CXX -TP -E -nologo"; ac_cv_prog_CXXCPP="$CXXCPP"; fi
-    if test -z "$LD"; then LD=link; fi
     if test -z "$AS"; then
         case "${target_cpu}" in
         i*86)
             AS=ml;
             ;;
         x86_64)
             AS=ml64;
             ;;

--- a/build/moz.configure/util.configure
+++ b/build/moz.configure/util.configure
@@ -56,36 +56,79 @@ def is_absolute_or_relative(path):
         return True
     return os.sep in path
 
 
 @imports(_import='mozpack.path', _as='mozpath')
 def normsep(path):
     return mozpath.normsep(path)
 
+
+@imports('ctypes')
+@imports(_from='ctypes', _import='wintypes')
+def get_GetShortPathNameW():
+    GetShortPathNameW = ctypes.windll.kernel32.GetShortPathNameW
+    GetShortPathNameW.argtypes = [wintypes.LPCWSTR, wintypes.LPWSTR,
+                                  wintypes.DWORD]
+    GetShortPathNameW.restype = wintypes.DWORD
+    return GetShortPathNameW
+
+
+@template
+@imports('ctypes')
+@imports('platform')
+@imports(_from='mozbuild.shellutil', _import='quote')
+def normalize_path():
+    # Until the build system can properly handle programs that need quoting,
+    # transform those paths into their short version on Windows (e.g.
+    # c:\PROGRA~1...).
+    if platform.system() == 'Windows':
+        GetShortPathNameW = get_GetShortPathNameW()
+
+        def normalize_path(path):
+            path = normsep(path)
+            if quote(path) == path:
+                return path
+            size = 0
+            while True:
+                out = ctypes.create_unicode_buffer(size)
+                needed = GetShortPathNameW(path, out, size)
+                if size >= needed:
+                    return normsep(out.value)
+                size = needed
+
+    else:
+        def normalize_path(path):
+            return normsep(path)
+
+    return normalize_path
+
+normalize_path = normalize_path()
+
+
 # Locates the given program using which, or returns the given path if it
 # exists.
 # The `paths` parameter may be passed to search the given paths instead of
 # $PATH.
 @imports(_from='which', _import='which')
 @imports(_from='which', _import='WhichError')
 @imports('itertools')
 @imports(_from='os', _import='pathsep')
 def find_program(file, paths=None):
     try:
         if is_absolute_or_relative(file):
-            return normsep(which(os.path.basename(file),
-                                 [os.path.dirname(file)]))
+            return normalize_path(which(os.path.basename(file),
+                                        [os.path.dirname(file)]))
         if paths:
             if not isinstance(paths, (list, tuple)):
                 die("Paths provided to find_program must be a list of strings, "
                     "not %r", paths)
             paths = list(itertools.chain(
                 *(p.split(pathsep) for p in paths if p)))
-        return normsep(which(file, path=paths))
+        return normalize_path(which(file, path=paths))
     except WhichError:
         return None
 
 
 @imports('os')
 @imports('subprocess')
 @imports(_from='mozbuild.configure.util', _import='LineIO')
 @imports(_from='tempfile', _import='mkstemp')

--- a/build/moz.configure/windows.configure
+++ b/build/moz.configure/windows.configure
@@ -45,41 +45,58 @@ def windows_sdk_dir(value, host):
 
     return tuple(x[1] for x in get_registry_values(
         r'HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Kits\Installed Roots'
         r'\KitsRoot*'))
 
 # The Windows SDK 8.1 and 10 have different layouts. The former has
 # $SDK/include/$subdir, while the latter has $SDK/include/$version/$subdir.
 # The vcvars* scripts don't actually care about the version, they just take
-# the last.
+# the last alphanumerically.
+# The $SDK/lib directories always have version subdirectories, but while the
+# versions match the one in $SDK/include for SDK 10, it's "winv6.3" for SDK
+# 8.1.
 @imports('os')
 @imports('re')
 @imports(_from='__builtin__', _import='sorted')
 @imports(_from='__builtin__', _import='WindowsError')
-def get_include_dir(sdk, subdir):
-    base = os.path.join(sdk, 'include')
-    try:
-        subdirs = [d for d in os.listdir(base)
-                   if os.path.isdir(os.path.join(base, d))]
-    except WindowsError:
-        subdirs = []
-    if not subdirs:
-        return None
-    if subdir in subdirs:
-        return os.path.join(base, subdir)
-    # At this point, either we have an incomplete or invalid SDK directory,
-    # or we exclusively have version numbers in subdirs.
-    versions = sorted((Version(d) for d in subdirs), reverse=True)
-    # Version('non-number').major is 0, so if the biggest version we have is
-    # 0, we have a problem.
-    if versions[0].major == 0:
-        return None
-    path = os.path.join(base, str(versions[0]), subdir)
-    return path if os.path.isdir(path) else None
+def get_sdk_dirs(sdk, subdir):
+    def get_dirs_containing(sdk, stem, subdir):
+        base = os.path.join(sdk, stem)
+        try:
+            subdirs = [d for d in os.listdir(base)
+                       if os.path.isdir(os.path.join(base, d))]
+        except WindowsError:
+            subdirs = []
+        if not subdirs:
+            return ()
+        if subdir in subdirs:
+            return (base,)
+        # At this point, either we have an incomplete or invalid SDK directory,
+        # or we exclusively have version numbers in subdirs.
+        return tuple(os.path.join(base, s) for s in subdirs
+                     if os.path.isdir(os.path.join(base, s, subdir)))
+
+    def categorize(dirs):
+        return {os.path.basename(d): d for d in dirs}
+
+    include_dirs = categorize(get_dirs_containing(sdk, 'include', subdir))
+    lib_dirs = categorize(get_dirs_containing(sdk, 'lib', subdir))
+
+    if 'include' in include_dirs:
+        include_dirs['winv6.3'] = include_dirs['include']
+        del include_dirs['include']
+
+    valid_versions = sorted(set(include_dirs) & set(lib_dirs), reverse=True)
+    if valid_versions:
+        return namespace(
+            path=sdk,
+            lib=lib_dirs[valid_versions[0]],
+            include=include_dirs[valid_versions[0]],
+        )
 
 
 @imports(_from='mozbuild.shellutil', _import='quote')
 def valid_windows_sdk_dir_result(value):
     if value:
         return '0x%04x in %s' % (value.version, quote(value.path))
 
 @depends_win(c_compiler, windows_sdk_dir, valid_windows_version,
@@ -88,74 +105,237 @@ def valid_windows_sdk_dir_result(value):
 @imports(_from='__builtin__', _import='sorted')
 @imports(_from='textwrap', _import='dedent')
 def valid_windows_sdk_dir(compiler, windows_sdk_dir, target_version,
                           windows_sdk_dir_env):
     if windows_sdk_dir_env:
         windows_sdk_dir_env = windows_sdk_dir_env[0]
     sdks = {}
     for d in windows_sdk_dir:
-        um_dir = get_include_dir(d, 'um')
-        shared_dir = get_include_dir(d, 'shared')
-        if um_dir and shared_dir:
+        sdk = get_sdk_dirs(d, 'um')
+        if sdk:
             check = dedent('''\
             #include <winsdkver.h>
             WINVER_MAXVER
             ''')
+            um_dir = os.path.join(sdk.include, 'um')
+            shared_dir = os.path.join(sdk.include, 'shared')
             result = try_preprocess(compiler.wrapper + [compiler.compiler] +
                                     compiler.flags +
                                     ['-I', um_dir, '-I', shared_dir], 'C',
                                     check)
             if result:
                 maxver = result.splitlines()[-1]
                 try:
                     maxver = int(maxver, 0)
                 except:
                     pass
                 else:
-                    sdks[d] = maxver
+                    sdks[d] = maxver, sdk
                     continue
         if d == windows_sdk_dir_env:
             raise FatalCheckError(
                 'Error while checking the version of the SDK in '
                 'WINDOWSSDKDIR (%s). Please verify it contains a valid and '
                 'complete SDK installation.' % windows_sdk_dir_env)
 
-    valid_sdks = sorted(sdks, key=lambda x: sdks[x], reverse=True)
+    valid_sdks = sorted(sdks, key=lambda x: sdks[x][0], reverse=True)
     if valid_sdks:
-        biggest_version = sdks[valid_sdks[0]]
+        biggest_version, sdk = sdks[valid_sdks[0]]
     if not valid_sdks or biggest_version < target_version:
         if windows_sdk_dir_env:
             raise FatalCheckError(
                 'You are targeting Windows version 0x%04x, but your SDK only '
                 'supports up to version 0x%04x. Install and use an updated SDK, '
                 'or target a lower version using --with-windows-version. '
                 'Alternatively, try running the Windows SDK Configuration Tool '
                 'and selecting a newer SDK. See '
                 'https://developer.mozilla.org/En/Windows_SDK_versions for '
                 'details on fixing this.' % (target_version, biggest_version))
 
         raise FatalCheckError(
             'Cannot find a Windows SDK for version >= 0x%04x.' % target_version)
 
     return namespace(
-        path=valid_sdks[0],
+        path=sdk.path,
+        include=sdk.include,
+        lib=sdk.lib,
         version=biggest_version,
     )
 
 
 add_old_configure_assignment(
     'WINDOWSSDKDIR',
     delayed_getattr(valid_windows_sdk_dir, 'path'))
 add_old_configure_assignment(
     'MOZ_WINSDK_MAXVER',
     depends(valid_windows_sdk_dir)(
         lambda x: '0x%04X0000' % x.version if x else None))
 
 
+@imports(_from='mozbuild.shellutil', _import='quote')
+def valid_ucrt_sdk_dir_result(value):
+    if value:
+        return '%s in %s' % (value.version, quote(value.path))
+
+@depends_win(windows_sdk_dir, 'WINDOWSSDKDIR')
+@checking('for Universal CRT SDK', valid_ucrt_sdk_dir_result)
+@imports(_from='__builtin__', _import='sorted')
+def valid_ucrt_sdk_dir(windows_sdk_dir, windows_sdk_dir_env):
+    if windows_sdk_dir_env:
+        windows_sdk_dir_env = windows_sdk_dir_env[0]
+    sdks = {}
+    for d in windows_sdk_dir:
+        sdk = get_sdk_dirs(d, 'ucrt')
+        if sdk:
+            version = os.path.basename(sdk.include)
+            # We're supposed to always find a version in the directory, because
+            # the 8.1 SDK, which doesn't have a version in the directory, doesn't
+            # contain the Universal CRT SDK. When the main SDK is 8.1, there
+            # is, however, supposed to be a reduced install of the SDK 10
+            # with the UCRT.
+            if version != 'include':
+                sdks[d] = Version(version), sdk
+                continue
+        if d == windows_sdk_dir_env:
+            raise FatalCheckError(
+                'The SDK in WINDOWSSDKDIR (%s) does not contain the Universal '
+                'CRT.' % windows_sdk_dir_env)
+
+    valid_sdks = sorted(sdks, key=lambda x: sdks[x][0], reverse=True)
+    if not valid_sdks:
+        raise FatalCheckError('Cannot find the Universal CRT SDK. '
+                              'Please install it.')
+
+    version, sdk = sdks[valid_sdks[0]]
+
+    return namespace(
+        path=sdk.path,
+        include=sdk.include,
+        lib=sdk.lib,
+        version=version,
+    )
+
+
+@depends_win(c_compiler)
+@imports('os')
+def vc_path(c_compiler):
+    if c_compiler.type != 'msvc':
+        return
+    # Normally, we'd start from c_compiler.compiler, but for now, it's not the
+    # ideal full path to the compiler. At least, we're guaranteed find_program
+    # will get us the one we found in toolchain.configure.
+    cl = find_program(c_compiler.compiler)
+    result = os.path.dirname(cl)
+    while True:
+        next, p = os.path.split(result)
+        if next == result:
+            die('Cannot determine the Visual C++ directory the compiler (%s) '
+                'is in' % cl)
+        result = next
+        if p.lower() == 'bin':
+            break
+    return result
+
+
+@depends_win(vc_path)
+@checking('for the Debug Interface Access SDK', lambda x: x or 'not found')
+def dia_sdk_dir(vc_path):
+    if vc_path:
+        path = os.path.join(os.path.dirname(vc_path), 'DIA SDK')
+        if os.path.isdir(path):
+            return path
+
+
+@depends_win(vc_path, valid_windows_sdk_dir, valid_ucrt_sdk_dir, dia_sdk_dir)
+@imports('os')
+def include_path(vc_path, windows_sdk_dir, ucrt_sdk_dir, dia_sdk_dir):
+    if not vc_path:
+        return
+    atlmfc_dir = os.path.join(vc_path, 'atlmfc', 'include')
+    if not os.path.isdir(atlmfc_dir):
+        die('Cannot find the ATL/MFC headers in the Visual C++ directory (%s). '
+            'Please install them.' % vc_path)
+
+    winrt_dir = os.path.join(windows_sdk_dir.include, 'winrt')
+    if not os.path.isdir(winrt_dir):
+        die('Cannot find the WinRT headers in the Windows SDK directory (%s). '
+            'Please install them.' % windows_sdk_dir.path)
+
+    includes = []
+    include_env = os.environ.get('INCLUDE')
+    if include_env:
+        includes.append(include_env)
+    includes.extend((
+        os.path.join(vc_path, 'include'),
+        atlmfc_dir,
+        os.path.join(windows_sdk_dir.include, 'shared'),
+        os.path.join(windows_sdk_dir.include, 'um'),
+        winrt_dir,
+        os.path.join(ucrt_sdk_dir.include, 'ucrt'),
+    ))
+    if dia_sdk_dir:
+        includes.append(os.path.join(dia_sdk_dir, 'include'))
+    # Set in the environment for old-configure
+    includes = os.pathsep.join(includes)
+    os.environ['INCLUDE'] = includes
+    return includes
+
+set_config('INCLUDE', include_path)
+
+
+@depends_win(target, vc_path, valid_windows_sdk_dir, valid_ucrt_sdk_dir, dia_sdk_dir)
+@imports('os')
+def lib_path(target, vc_path, windows_sdk_dir, ucrt_sdk_dir, dia_sdk_dir):
+    if not vc_path:
+        return
+    vc_target = {
+        'x86': '',
+        'x86_64': 'amd64',
+        'arm': 'arm',
+    }.get(target.cpu)
+    if vc_target is None:
+        return
+    # As vc_target can be '', and os.path.join will happily use the empty
+    # string, leading to a string ending with a backslash, that Make will
+    # interpret as a "string continues on next line" indicator, use variable
+    # args.
+    vc_target = (vc_target,) if vc_target else ()
+    sdk_target = {
+        'x86': 'x86',
+        'x86_64': 'x64',
+        'arm': 'arm',
+    }.get(target.cpu)
+
+    atlmfc_dir = os.path.join(vc_path, 'atlmfc', 'lib', *vc_target)
+    if not os.path.isdir(atlmfc_dir):
+        die('Cannot find the ATL/MFC libraries in the Visual C++ directory (%s). '
+            'Please install them.' % vc_path)
+
+
+    libs = []
+    lib_env = os.environ.get('LIB')
+    if lib_env:
+        libs.append(lib_env)
+    libs.extend((
+        os.path.join(vc_path, 'lib', *vc_target),
+        atlmfc_dir,
+        os.path.join(windows_sdk_dir.lib, 'um', sdk_target),
+        os.path.join(ucrt_sdk_dir.lib, 'ucrt', sdk_target),
+    ))
+    if dia_sdk_dir:
+        libs.append(os.path.join(dia_sdk_dir, 'lib', *vc_target))
+    # Set in the environment for old-configure
+    libs = os.pathsep.join(libs)
+    os.environ['LIB'] = libs
+    return libs
+
+set_config('LIB', lib_path)
+
+
 option(env='MT', nargs=1, help='Path to the Microsoft Manifest Tool')
 
 @depends_win(valid_windows_sdk_dir)
 @imports(_from='os', _import='environ')
 @imports('platform')
 def sdk_bin_path(valid_windows_sdk_dir):
     if not valid_windows_sdk_dir:
         return
@@ -170,20 +350,18 @@ def sdk_bin_path(valid_windows_sdk_dir):
         os.path.join(valid_windows_sdk_dir.path, 'bin', vc_host)
     ]
     if vc_host == 'x64':
         result.append(
             os.path.join(valid_windows_sdk_dir.path, 'bin', 'x86'))
     return result
 
 
-# Normally, we'd use `MT` instead of `_MT`, but for now, we want MT to only contain
-# mt.exe.
-mt = check_prog('_MT', depends_win()(lambda: ('mt.exe',)), what='mt',
-                input='MT', paths=sdk_bin_path)
+mt = check_prog('MT', depends_win()(lambda: ('mt.exe',)), input='MT',
+                paths=sdk_bin_path)
 
 
 # Check that MT is not something unexpected like "magnetic tape manipulation
 # utility".
 @depends_win(mt)
 @checking('whether MT is really Microsoft Manifest Tool', lambda x: bool(x))
 @imports('subprocess')
 def valid_mt(path):
@@ -193,20 +371,29 @@ def valid_mt(path):
                         if 'Microsoft (R) Manifest Tool' in l)
         if out:
               return path
     except subprocess.CalledProcessError:
         pass
     raise FatalCheckError('%s is not Microsoft Manifest Tool')
 
 
-set_config('MT', depends_if(valid_mt)(lambda x: os.path.basename(x)))
 set_config('MSMANIFEST_TOOL', depends(valid_mt)(lambda x: bool(x)))
 
 
+# Ultimately, this will move to toolchain.configure and be turned into a
+# cross-platform check.
+option(env='LD', nargs=1, help='Path to the linker')
+
+link = check_prog('LINK', depends_win()(lambda: ('link.exe',)), input='LD',
+                  paths=vc_compiler_path)
+
+add_old_configure_assignment('LD', depends_win(link)(lambda x: x))
+
+
 # Normally, we'd just have CC, etc. set to absolute paths, but the build system
 # doesn't currently handle properly the case where the paths contain spaces.
 # Additionally, there's the issue described in toolchain.configure, in
 # valid_compiler().
 @depends_win(sdk_bin_path)
 @imports('os')
 def alter_path(sdk_bin_path):
     path = os.pathsep.join(sdk_bin_path)

--- a/build/win32/mozconfig.vs2015-win64
+++ b/build/win32/mozconfig.vs2015-win64
@@ -1,23 +1,25 @@
 if [ -z "${VSPATH}" ]; then
     TOOLTOOL_DIR=${TOOLTOOL_DIR:-$topsrcdir}
     VSPATH="$(cd ${TOOLTOOL_DIR} && pwd)/vs2015u2"
-    VSWINPATH="$(cd ${TOOLTOOL_DIR} && pwd -W)/vs2015u2"
 fi
 
+VSWINPATH="$(cd ${VSPATH} && pwd -W)"
+
 export WINDOWSSDKDIR="${VSWINPATH}/SDK"
 export WIN32_REDIST_DIR="${VSPATH}/VC/redist/x86/Microsoft.VC140.CRT"
 export WIN_UCRT_REDIST_DIR="${VSPATH}/SDK/Redist/ucrt/DLLs/x86"
 
-export PATH="${VSPATH}/VC/bin/amd64_x86:${VSPATH}/VC/bin/amd64:${VSPATH}/VC/bin:${VSPATH}/SDK/bin/x86:${VSPATH}/SDK/bin/x64:${VSPATH}/DIASDK/bin:${PATH}"
+export PATH="${VSPATH}/VC/bin/amd64_x86:${VSPATH}/VC/bin/amd64:${VSPATH}/VC/bin:${VSPATH}/SDK/bin/x86:${VSPATH}/SDK/bin/x64:${VSPATH}/DIA SDK/bin:${PATH}"
 export PATH="${VSPATH}/VC/redist/x86/Microsoft.VC140.CRT:${VSPATH}/VC/redist/x64/Microsoft.VC140.CRT:${VSPATH}/SDK/Redist/ucrt/DLLs/x86:${VSPATH}/SDK/Redist/ucrt/DLLs/x64:${PATH}"
 
-export INCLUDE="${VSPATH}/VC/include:${VSPATH}/VC/atlmfc/include:${VSPATH}/SDK/Include/ucrt:${VSPATH}/SDK/Include/shared:${VSPATH}/SDK/Include/um:${VSPATH}/SDK/Include/winrt:${VSPATH}/DIASDK/include"
-export LIB="${VSPATH}/VC/lib:${VSPATH}/VC/atlmfc/lib:${VSPATH}/SDK/lib/ucrt/x86:${VSPATH}/SDK/lib/um/x86:${VSPATH}/DIASDK/lib"
+export INCLUDE="${VSPATH}/VC/include:${VSPATH}/VC/atlmfc/include:${VSPATH}/SDK/Include/10.0.10586.0/ucrt:${VSPATH}/SDK/Include/10.0.10586.0/shared:${VSPATH}/SDK/Include/10.0.10586.0/um:${VSPATH}/SDK/Include/10.0.10586.0/winrt:${VSPATH}/DIA SDK/include"
+export LIB="${VSPATH}/VC/lib:${VSPATH}/VC/atlmfc/lib:${VSPATH}/SDK/lib/10.0.10586.0/ucrt/x86:${VSPATH}/SDK/lib/10.0.10586.0/um/x86:${VSPATH}/DIA SDK/lib"
 
 . $topsrcdir/build/mozconfig.vs-common
 
+mk_export_correct_style WINDOWSSDKDIR
 mk_export_correct_style INCLUDE
 mk_export_correct_style LIB
 mk_export_correct_style PATH
 mk_export_correct_style WIN32_REDIST_DIR
 mk_export_correct_style WIN_UCRT_REDIST_DIR

--- a/build/win64/mozconfig.vs2015
+++ b/build/win64/mozconfig.vs2015
@@ -1,22 +1,24 @@
 if [ -z "${VSPATH}" ]; then
     TOOLTOOL_DIR=${TOOLTOOL_DIR:-$topsrcdir}
     VSPATH="$(cd ${TOOLTOOL_DIR} && pwd)/vs2015u2"
-    VSWINPATH="$(cd ${TOOLTOOL_DIR} && pwd -W)/vs2015u2"
 fi
 
+VSWINPATH="$(cd ${VSPATH} && pwd -W)"
+
 export WINDOWSSDKDIR="${VSWINPATH}/SDK"
 export WIN32_REDIST_DIR=${VSPATH}/VC/redist/x64/Microsoft.VC140.CRT
 export WIN_UCRT_REDIST_DIR="${VSPATH}/SDK/Redist/ucrt/DLLs/x64"
 
-export PATH="${VSPATH}/VC/bin/amd64:${VSPATH}/VC/bin:${VSPATH}/SDK/bin/x64:${VSPATH}/VC/redist/x64/Microsoft.VC140.CRT:${VSPATH}/SDK/Redist/ucrt/DLLs/x64:${VSPATH}/DIASDK/bin/amd64:${PATH}"
+export PATH="${VSPATH}/VC/bin/amd64:${VSPATH}/VC/bin:${VSPATH}/SDK/bin/x64:${VSPATH}/VC/redist/x64/Microsoft.VC140.CRT:${VSPATH}/SDK/Redist/ucrt/DLLs/x64:${VSPATH}/DIA SDK/bin/amd64:${PATH}"
 
-export INCLUDE="${VSPATH}/VC/include:${VSPATH}/VC/atlmfc/include:${VSPATH}/SDK/Include/ucrt:${VSPATH}/SDK/Include/shared:${VSPATH}/SDK/Include/um:${VSPATH}/SDK/Include/winrt:${VSPATH}/DIASDK/include"
-export LIB="${VSPATH}/VC/lib/amd64:${VSPATH}/VC/atlmfc/lib/amd64:${VSPATH}/SDK/lib/ucrt/x64:${VSPATH}/SDK/lib/um/x64:${VSPATH}/DIASDK/lib/amd64"
+export INCLUDE="${VSPATH}/VC/include:${VSPATH}/VC/atlmfc/include:${VSPATH}/SDK/Include/10.0.10586.0/ucrt:${VSPATH}/SDK/Include/10.0.10586.0/shared:${VSPATH}/SDK/Include/10.0.10586.0/um:${VSPATH}/SDK/Include/10.0.10586.0/winrt:${VSPATH}/DIA SDK/include"
+export LIB="${VSPATH}/VC/lib/amd64:${VSPATH}/VC/atlmfc/lib/amd64:${VSPATH}/SDK/lib/10.0.10586.0/ucrt/x64:${VSPATH}/SDK/lib/10.0.10586.0/um/x64:${VSPATH}/DIA SDK/lib/amd64"
 
 . $topsrcdir/build/mozconfig.vs-common
 
+mk_export_correct_style WINDOWSSDKDIR
 mk_export_correct_style INCLUDE
 mk_export_correct_style LIB
 mk_export_correct_style PATH
 mk_export_correct_style WIN32_REDIST_DIR
 mk_export_correct_style WIN_UCRT_REDIST_DIR

--- a/build/windows_toolchain.py
+++ b/build/windows_toolchain.py
@@ -24,33 +24,28 @@ from mozpack.mozjar import (
 )
 import mozpack.path as mozpath
 
 
 # mozpack.match patterns for files under "Microsoft Visual Studio 14.0".
 VS_PATTERNS = [
     {
         'pattern': 'DIA SDK/bin/**',
-        # Various tools don't like spaces in filenames. So remove it.
-        'rewrite': [('DIA SDK/', 'DIASDK/')],
         'ignore': (
             'DIA SDK/bin/arm/**',
         ),
     },
     {
         'pattern': 'DIA SDK/idl/**',
-        'rewrite': [('DIA SDK/', 'DIASDK/')],
     },
     {
         'pattern': 'DIA SDK/include/**',
-        'rewrite': [('DIA SDK/', 'DIASDK/')],
     },
     {
         'pattern': 'DIA SDK/lib/**',
-        'rewrite': [('DIA SDK/', 'DIASDK/')],
         'ignore': (
             'DIA SDK/lib/arm/**',
         ),
     },
     # ATL is needed by Breakpad.
     {
         'pattern': 'VC/atlmfc/include/**',
     },
@@ -155,28 +150,22 @@ def resolve_files():
     vs_path, sdk_path = find_vs_paths()
 
     for entry in VS_PATTERNS:
         finder = FileFinder(vs_path, find_executables=False,
                             ignore=entry.get('ignore', []))
         for p, f in finder.find(entry['pattern']):
             assert p.startswith(('VC/', 'DIA SDK/'))
 
-            for source, dest in entry.get('rewrite', []):
-                p = p.replace(source, dest)
-
             yield p.encode('utf-8'), f
 
     for entry in SDK_PATTERNS:
         finder = FileFinder(sdk_path, find_executables=False,
                             ignore=entry.get('ignore', []))
         for p, f in finder.find(entry['pattern']):
-            # We remove the SDK version from the path so we don't have
-            # to update other configs when we change the SDK version.
-            p = p.replace('/%s/' % SDK_RELEASE, '/')
             relpath = 'SDK/%s' % p
 
             yield relpath.encode('utf-8'), f
 
 
 def resolve_files_and_hash(manifest):
     """Resolve files and hash their data.
 

--- a/config/config.mk
+++ b/config/config.mk
@@ -353,16 +353,28 @@ SDK_LIB_DIR = $(DIST)/sdk/lib
 SDK_BIN_DIR = $(DIST)/sdk/bin
 
 DEPENDENCIES	= .md
 
 ifdef MACOSX_DEPLOYMENT_TARGET
 export MACOSX_DEPLOYMENT_TARGET
 endif # MACOSX_DEPLOYMENT_TARGET
 
+# Export to propagate to cl and submake for third-party code.
+# Eventually, we'll want to just use -I.
+ifdef INCLUDE
+export INCLUDE
+endif
+
+# Export to propagate to link.exe and submake for third-party code.
+# Eventually, we'll want to just use -LIBPATH.
+ifdef LIB
+export LIB
+endif
+
 ifdef MOZ_USING_CCACHE
 ifdef CLANG_CXX
 export CCACHE_CPP2=1
 endif
 endif
 
 # Set link flags according to whether we want a console.
 ifeq ($(OS_ARCH),WINNT)

--- a/devtools/client/themes/toolbars.css
+++ b/devtools/client/themes/toolbars.css
@@ -243,16 +243,17 @@
 .devtools-button:disabled,
 .devtools-button[disabled],
 .devtools-toolbarbutton[disabled] {
   opacity: 0.5 !important;
 }
 
 .devtools-button[checked]:empty::before,
 .devtools-button[open]:empty::before,
+.devtools-button.checked::before,
 .devtools-toolbarbutton:not([label])[checked=true] > image,
 .devtools-toolbarbutton:not([label])[open=true] > image {
   filter: var(--checked-icon-filter);
 }
 
 /* Icon-and-text buttons */
 .devtools-toolbarbutton.icon-and-text .toolbarbutton-text {
   margin-inline-start: .5em !important;
@@ -303,16 +304,20 @@
 :root {
   --clear-icon-url: url("chrome://devtools/skin/images/clear.svg");
 }
 
 .devtools-button.devtools-clear-icon::before {
   background-image: var(--clear-icon-url);
 }
 
+.devtools-button.devtools-filter-icon::before {
+  background-image: var(--filter-image);
+}
+
 .devtools-toolbarbutton.devtools-clear-icon {
   list-style-image: var(--clear-icon-url);
 }
 
 .devtools-option-toolbarbutton {
   list-style-image: var(--tool-options-image);
 }
 
@@ -379,16 +384,25 @@
   visibility: hidden;
 }
 
 .devtools-searchinput .textbox-input::-moz-placeholder,
 .devtools-filterinput .textbox-input::-moz-placeholder {
   font-style: normal;
 }
 
+.devtools-plaininput {
+  border-color: transparent;
+  background-color: transparent;
+}
+
+.theme-dark .devtools-plaininput {
+  color: var(--theme-highlight-gray);
+}
+
 /* Searchbox is a div container element for a search input element */
 .devtools-searchbox {
   display: flex;
   flex: 1;
   height: 23px;
   position: relative;
   padding: 0 3px;
 }
@@ -644,8 +658,36 @@
 @keyframes throbber-spin {
   from {
     transform: none;
   }
   to {
     transform: rotate(360deg);
   }
 }
+
+/*
+ * Filter buttons
+ * @TODO : Fix when https://bugzilla.mozilla.org/show_bug.cgi?id=1255116 lands
+ */
+.menu-filter-button {
+  -moz-appearance: none;
+  background: rgba(128,128,128,0.1);
+  border: none;
+  border-radius: 2px;
+  min-width: 0;
+  padding: 0 5px;
+  margin: 2px;
+  color: var(--theme-body-color);
+}
+
+.menu-filter-button:hover {
+  background: rgba(128,128,128,0.2);
+}
+
+.menu-filter-button:hover:active {
+  background-color: var(--theme-selection-background-semitransparent);
+}
+
+.menu-filter-button:not(:active).checked {
+  background-color: var(--theme-selection-background);
+  color: var(--theme-selection-color);
+}

--- a/devtools/client/themes/webconsole.css
+++ b/devtools/client/themes/webconsole.css
@@ -146,16 +146,17 @@ a {
   display: block;
   flex: auto;
 }
 
 #output-wrapper {
   direction: ltr;
   overflow: auto;
   -moz-user-select: text;
+  position: relative;
 }
 
 /* The width on #output-container is set to a hardcoded px in webconsole.js
    since it's way faster than using 100% with -moz-box-flex (see Bug 1237368) */
 
 #output-container.hideTimestamps > .message {
   padding-inline-start: 0;
   margin-inline-start: 7px;
@@ -619,8 +620,46 @@ a.learn-more-link.webconsole-learn-more-
 
 .theme-firebug .consoletable .theme-body {
   width: 100%;
   border-top: 1px solid #D7D7D7;
   border-bottom: 2px solid #D7D7D7;
   border-left: 1px solid #D7D7D7;
   border-right: 1px solid #D7D7D7;
 }
+
+
+/* NEW CONSOLE STYLES */
+
+#output-wrapper > div {
+  position: absolute;
+  top: 0;
+  bottom: 0;
+  left: 0;
+  right: 0;
+}
+
+#output-container {
+  height: 100%;
+}
+
+.webconsole-output-wrapper {
+  display: flex;
+  flex-direction: column;
+  height: 100%;
+}
+
+.webconsole-filterbar-wrapper {
+  flex-grow: 0;
+}
+
+.webconsole-output {
+  flex: 1;
+  overflow: auto;
+}
+
+.webconsole-filterbar-primary {
+  display: flex;
+}
+
+.webconsole-filterbar-primary .devtools-plaininput {
+  flex: 1 1 100%;
+}

--- a/devtools/client/webconsole/new-console-output/actions/messages.js
+++ b/devtools/client/webconsole/new-console-output/actions/messages.js
@@ -8,26 +8,53 @@
 
 const {
   prepareMessage
 } = require("devtools/client/webconsole/new-console-output/utils/messages");
 
 const {
   MESSAGE_ADD,
   MESSAGES_CLEAR,
+  SEVERITY_FILTER,
+  MESSAGES_SEARCH,
+  FILTERS_CLEAR,
 } = require("../constants");
 
 function messageAdd(packet) {
   let message = prepareMessage(packet);
   return {
     type: MESSAGE_ADD,
     message
   };
 }
 
 function messagesClear() {
   return {
     type: MESSAGES_CLEAR
   };
 }
 
+function severityFilter(filter, toggled) {
+  return {
+    type: SEVERITY_FILTER,
+    filter,
+    toggled
+  };
+}
+
+function filtersClear() {
+  return {
+    type: FILTERS_CLEAR
+  };
+}
+
+function messagesSearch(searchText) {
+  return {
+    type: MESSAGES_SEARCH,
+    searchText
+  };
+}
+
 exports.messageAdd = messageAdd;
 exports.messagesClear = messagesClear;
+exports.severityFilter = severityFilter;
+exports.filtersClear = filtersClear;
+exports.messagesSearch = messagesSearch;

--- a/devtools/client/webconsole/new-console-output/actions/moz.build
+++ b/devtools/client/webconsole/new-console-output/actions/moz.build
@@ -1,8 +1,9 @@
 # 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/.
 
 DevToolsModules(
     'messages.js',
+    'ui.js',
 )

new file mode 100644
--- /dev/null
+++ b/devtools/client/webconsole/new-console-output/actions/ui.js
@@ -0,0 +1,19 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ft=javascript ts=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/. */
+
+"use strict";
+
+const {
+  FILTERBAR_TOGGLE,
+} = require("../constants");
+
+function filterBarToggle(show) {
+  return {
+    type: FILTERBAR_TOGGLE
+  };
+}
+
+exports.filterBarToggle = filterBarToggle;

--- a/devtools/client/webconsole/new-console-output/components/console-output.js
+++ b/devtools/client/webconsole/new-console-output/components/console-output.js
@@ -22,38 +22,37 @@ const ConsoleOutput = createClass({
     // This function is created in mergeProps
     openVariablesView: PropTypes.func.isRequired,
     messages: PropTypes.array.isRequired
   },
 
   displayName: "ConsoleOutput",
 
   componentWillUpdate() {
-    // @TODO Move this to a parent component.
-    let node = ReactDOM.findDOMNode(this).parentNode.parentNode.parentNode;
+    let node = ReactDOM.findDOMNode(this);
     if (node.lastChild) {
       this.shouldScrollBottom = isScrolledToBottom(node.lastChild, node);
     }
   },
 
   componentDidUpdate() {
     if (this.shouldScrollBottom) {
-      let node = ReactDOM.findDOMNode(this).parentNode.parentNode.parentNode;
+      let node = ReactDOM.findDOMNode(this);
       node.scrollTop = node.scrollHeight;
     }
   },
 
   render() {
     let messageNodes = this.props.messages.map(function (message) {
       return (
         MessageContainer({ message })
       );
     });
     return (
-      dom.div({}, messageNodes)
+      dom.div({className: "webconsole-output"}, messageNodes)
     );
   }
 });
 
 function isScrolledToBottom(outputNode, scrollNode) {
   let lastNodeHeight = outputNode.lastChild ?
                        outputNode.lastChild.clientHeight : 0;
   return scrollNode.scrollTop + scrollNode.clientHeight >=

new file mode 100644
--- /dev/null
+++ b/devtools/client/webconsole/new-console-output/components/filter-bar.js
@@ -0,0 +1,133 @@
+/* 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/. */
+"use strict";
+
+const {
+  createFactory,
+  createClass,
+  DOM: dom,
+  PropTypes
+} = require("devtools/client/shared/vendor/react");
+const { connect } = require("devtools/client/shared/vendor/react-redux");
+const { getAllFilters } = require("devtools/client/webconsole/new-console-output/selectors/filters");
+const { getAllUi } = require("devtools/client/webconsole/new-console-output/selectors/ui");
+const messagesActions = require("devtools/client/webconsole/new-console-output/actions/messages");
+const uiActions = require("devtools/client/webconsole/new-console-output/actions/ui");
+const { store } = require("devtools/client/webconsole/new-console-output/store");
+const {
+  SEVERITY_FILTER
+} = require("../constants");
+const FilterToggleButton = createFactory(require("devtools/client/webconsole/new-console-output/components/filter-toggle-button").FilterToggleButton);
+
+const FilterBar = createClass({
+
+  displayName: "FilterBar",
+
+  propTypes: {
+    filter: PropTypes.object.isRequired,
+    ui: PropTypes.object.isRequired
+  },
+
+  onClearOutputButtonClick: function () {
+    store.dispatch(messagesActions.messagesClear());
+  },
+
+  onToggleFilterConfigBarButtonClick: function () {
+    store.dispatch(uiActions.filterBarToggle());
+  },
+
+  onClearFiltersButtonClick: function () {
+    store.dispatch(messagesActions.filtersClear());
+  },
+
+  onSearchInput: function (e) {
+    store.dispatch(messagesActions.messagesSearch(e.target.value));
+  },
+
+  render() {
+    const {filter, ui} = this.props;
+    let configFilterBarVisible = ui.configFilterBarVisible;
+    let children = [];
+
+    children.push(dom.div({className: "devtools-toolbar webconsole-filterbar-primary"},
+      dom.button({
+        className: "devtools-button devtools-clear-icon",
+        title: "Clear output",
+        onClick: this.onClearOutputButtonClick
+      }),
+      dom.button({
+        className: "devtools-button devtools-filter-icon" + (
+          configFilterBarVisible ? " checked" : ""),
+        title: "Toggle filter bar",
+        onClick: this.onToggleFilterConfigBarButtonClick
+      }),
+      dom.input({
+        className: "devtools-plaininput",
+        type: "search",
+        value: filter.searchText,
+        placeholder: "Filter output",
+        onInput: this.onSearchInput
+      })
+    ));
+
+    if (configFilterBarVisible) {
+      children.push(
+        dom.div({className: "devtools-toolbar"},
+          FilterToggleButton({
+            active: filter.error,
+            label: "Errors",
+            filterType: SEVERITY_FILTER,
+            filterKey: "error"}),
+          FilterToggleButton({
+            active: filter.warn,
+            label: "Warnings",
+            filterType: SEVERITY_FILTER,
+            filterKey: "warn"}),
+          FilterToggleButton({
+            active: filter.log,
+            label: "Logs",
+            filterType: SEVERITY_FILTER,
+            filterKey: "log"}),
+          FilterToggleButton({
+            active: filter.info,
+            label: "Info",
+            filterType: SEVERITY_FILTER,
+            filterKey: "info"})
+        )
+      );
+    }
+
+    if (ui.filteredMessageVisible) {
+      children.push(
+        dom.div({className: "devtools-toolbar"},
+          dom.span({
+            className: "clear"},
+            "You have filters set that may hide some results. " +
+            "Learn more about our filtering syntax ",
+            dom.a({}, "here"),
+            "."),
+          dom.button({
+            className: "menu-filter-button",
+            onClick: this.onClearFiltersButtonClick
+          }, "Remove filters")
+        )
+      );
+    }
+
+    return (
+      dom.div({className: "webconsole-filteringbar-wrapper"},
+        children
+      )
+    );
+  }
+});
+
+function mapStateToProps(state) {
+  return {
+    filter: getAllFilters(state),
+    ui: getAllUi(state)
+  };
+}
+
+module.exports = connect(mapStateToProps)(FilterBar);

new file mode 100644
--- /dev/null
+++ b/devtools/client/webconsole/new-console-output/components/filter-toggle-button.js
@@ -0,0 +1,50 @@
+/* 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/. */
+"use strict";
+
+const {
+  createClass,
+  DOM: dom,
+  PropTypes
+} = require("devtools/client/shared/vendor/react");
+const { store } = require("devtools/client/webconsole/new-console-output/store");
+const actions = require("devtools/client/webconsole/new-console-output/actions/messages");
+const {
+  SEVERITY_FILTER
+} = require("../constants");
+
+const FilterToggleButton = createClass({
+
+  displayName: "FilterToggleButton",
+
+  propTypes: {
+    label: PropTypes.string.isRequired,
+    filterType: PropTypes.string.isRequired,
+    filterKey: PropTypes.string.isRequired,
+    active: PropTypes.bool.isRequired,
+  },
+
+  onClick: function () {
+    if (this.props.filterType === SEVERITY_FILTER) {
+      store.dispatch(actions.severityFilter(
+        this.props.filterKey, !this.props.active));
+    }
+  },
+
+  render() {
+    const {label, active} = this.props;
+
+    let classList = ["menu-filter-button"];
+    if (active) {
+      classList.push("checked");
+    }
+
+    return dom.button({
+      className: classList.join(" "),
+      onClick: this.onClick
+    }, label);
+  }
+});
+
+exports.FilterToggleButton = FilterToggleButton;

--- a/devtools/client/webconsole/new-console-output/components/message-container.js
+++ b/devtools/client/webconsole/new-console-output/components/message-container.js
@@ -28,16 +28,20 @@ const componentMap = new Map([
 
 const MessageContainer = createClass({
   displayName: "MessageContainer",
 
   propTypes: {
     message: PropTypes.object.isRequired
   },
 
+  shouldComponentUpdate(nextProps, nextState) {
+    return this.props.message.repeat !== nextProps.message.repeat;
+  },
+
   render() {
     const { message } = this.props;
     let MessageComponent = createFactory(getMessageComponent(message));
     return MessageComponent({ message });
   }
 });
 
 function getMessageComponent(message) {

--- a/devtools/client/webconsole/new-console-output/components/moz.build
+++ b/devtools/client/webconsole/new-console-output/components/moz.build
@@ -4,14 +4,16 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 DIRS += [
     'message-types'
 ]
 
 DevToolsModules(
     'console-output.js',
+    'filter-bar.js',
+    'filter-toggle-button.js',
     'grip-message-body.js',
     'message-container.js',
     'message-icon.js',
     'message-repeat.js',
     'variables-view-link.js'
 )

--- a/devtools/client/webconsole/new-console-output/constants.js
+++ b/devtools/client/webconsole/new-console-output/constants.js
@@ -3,16 +3,20 @@
 /* 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/. */
 "use strict";
 
 const actionTypes = {
   MESSAGE_ADD: "MESSAGE_ADD",
   MESSAGES_CLEAR: "MESSAGES_CLEAR",
+  SEVERITY_FILTER: "SEVERITY_FILTER",
+  MESSAGES_SEARCH: "MESSAGES_SEARCH",
+  FILTERS_CLEAR: "FILTERS_CLEAR",
+  FILTERBAR_TOGGLE: "FILTERBAR_TOGGLE",
 };
 
 const categories = {
   CATEGORY_NETWORK: "network",
   CATEGORY_CSS: "cssparser",
   CATEGORY_JS: "exception",
   CATEGORY_WEBDEV: "console",
   CATEGORY_INPUT: "input",
@@ -87,11 +91,15 @@ const chromeRDPEnums = {
     LOG: "log",
     ERROR: "error",
     WARN: "warn",
     DEBUG: "debug",
     INFO: "info"
   }
 };
 
+const filterTypes = {
+  SEVERITY_FILTER: "SEVERITY_FILTER"
+};
+
 // Combine into a single constants object
 module.exports = Object.assign({}, actionTypes, categories, severities, levels,
-  chromeRDPEnums);
+  chromeRDPEnums, filterTypes);