--- a/browser/base/content/browser-tabPreviews.js
+++ b/browser/base/content/browser-tabPreviews.js
@@ -42,16 +42,20 @@ var tabPreviews = {
       img.src = PageThumbs.getThumbnailURL(uri);
       return img;
     }
 
     return this.capture(aTab, !aTab.hasAttribute("busy"));
   },
 
   capture: function tabPreviews_capture(aTab, aShouldCache) {
+    // Bug 863512 - Make page thumbnails work in electrolysis
+    if (gMultiProcessBrowser)
+      return new Image();
+
     let browser = aTab.linkedBrowser;
     let uri = browser.currentURI.spec;
 
     // FIXME: The gBrowserThumbnails._shouldCapture determines whether
     //        thumbnails should be written to disk. This should somehow be part
     //        of the PageThumbs API. (bug 1062414)
     if (aShouldCache &&
         gBrowserThumbnails._shouldCapture(browser)) {
@@ -68,17 +72,17 @@ var tabPreviews = {
 
     let canvas = PageThumbs.createCanvas(window);
 
     if (aShouldCache) {
       aTab.__thumbnail = canvas;
       aTab.__thumbnail_lastURI = uri;
     }
 
-    PageThumbs.captureToCanvas(browser, canvas);
+    PageThumbs.captureToCanvas(aTab.linkedBrowser.contentWindow, canvas);
     return canvas;
   },
 
   handleEvent: function tabPreviews_handleEvent(event) {
     switch (event.type) {
       case "TabSelect":
         if (this._selectedTab &&
             this._selectedTab.parentNode &&

--- a/browser/base/content/browser-thumbnails.js
+++ b/browser/base/content/browser-thumbnails.js
@@ -28,31 +28,39 @@ let gBrowserThumbnails = {
   _timeouts: null,
 
   /**
    * List of tab events we want to listen for.
    */
   _tabEvents: ["TabClose", "TabSelect"],
 
   init: function Thumbnails_init() {
+    // Bug 863512 - Make page thumbnails work in electrolysis
+    if (gMultiProcessBrowser)
+      return;
+
     PageThumbs.addExpirationFilter(this);
     gBrowser.addTabsProgressListener(this);
     Services.prefs.addObserver(this.PREF_DISK_CACHE_SSL, this, false);
 
     this._sslDiskCacheEnabled =
       Services.prefs.getBoolPref(this.PREF_DISK_CACHE_SSL);
 
     this._tabEvents.forEach(function (aEvent) {
       gBrowser.tabContainer.addEventListener(aEvent, this, false);
     }, this);
 
     this._timeouts = new WeakMap();
   },
 
   uninit: function Thumbnails_uninit() {
+    // Bug 863512 - Make page thumbnails work in electrolysis
+    if (gMultiProcessBrowser)
+      return;
+
     PageThumbs.removeExpirationFilter(this);
     gBrowser.removeTabsProgressListener(this);
     Services.prefs.removeObserver(this.PREF_DISK_CACHE_SSL, this);
 
     this._tabEvents.forEach(function (aEvent) {
       gBrowser.tabContainer.removeEventListener(aEvent, this, false);
     }, this);
   },
@@ -112,41 +120,41 @@ let gBrowserThumbnails = {
       this._capture(aBrowser);
     }.bind(this), this._captureDelayMS);
 
     this._timeouts.set(aBrowser, timeout);
   },
 
   // FIXME: This should be part of the PageThumbs API. (bug 1062414)
   _shouldCapture: function Thumbnails_shouldCapture(aBrowser) {
+    // Don't try to capture in e10s yet (because of bug 698371)
+    if (gMultiProcessBrowser)
+      return false;
+
     // Capture only if it's the currently selected tab.
     if (aBrowser != gBrowser.selectedBrowser)
       return false;
 
     // Don't capture in per-window private browsing mode.
     if (PrivateBrowsingUtils.isWindowPrivate(window))
       return false;
 
     let doc = aBrowser.contentDocument;
 
     // FIXME Bug 720575 - Don't capture thumbnails for SVG or XML documents as
     //       that currently regresses Talos SVG tests.
     if (doc instanceof SVGDocument || doc instanceof XMLDocument)
       return false;
 
-    // Don't take screenshots of about: pages.
-    if (aBrowser.currentURI.schemeIs("about"))
+    // There's no point in taking screenshot of loading pages.
+    if (aBrowser.docShell.busyFlags != Ci.nsIDocShell.BUSY_FLAGS_NONE)
       return false;
 
-    // FIXME e10s work around, we need channel information. bug 1073957
-    if (!aBrowser.docShell)
-      return true;
-
-    // There's no point in taking screenshot of loading pages.
-    if (aBrowser.docShell.busyFlags != Ci.nsIDocShell.BUSY_FLAGS_NONE)
+    // Don't take screenshots of about: pages.
+    if (aBrowser.currentURI.schemeIs("about"))
       return false;
 
     let channel = aBrowser.docShell.currentDocumentChannel;
 
     // No valid document channel. We shouldn't take a screenshot.
     if (!channel)
       return false;
 

--- a/browser/base/content/socialchat.xml
+++ b/browser/base/content/socialchat.xml
@@ -702,17 +702,17 @@
         // canvas size (in CSS pixels) to the window's backing resolution in order
         // to get a full-resolution drag image for use on HiDPI displays.
         let windowUtils = window.getInterface(Ci.nsIDOMWindowUtils);
         let scale = windowUtils.screenPixelsPerCSSPixel / windowUtils.fullZoom;
         let canvas = document.createElementNS("http://www.w3.org/1999/xhtml", "canvas");
         canvas.mozOpaque = true;
         canvas.width = 160 * scale;
         canvas.height = 90 * scale;
-        PageThumbs.captureToCanvas(chatbox, canvas);
+        PageThumbs.captureToCanvas(chatbox.contentWindow, canvas);
         dt.setDragImage(canvas, -16 * scale, -16 * scale);
 
         event.stopPropagation();
       ]]></handler>
 
       <handler event="dragend"><![CDATA[
         let dt = event.dataTransfer;
         let draggedChat = dt.mozGetDataAt("application/x-moz-chatbox", 0);

--- a/browser/base/content/tabbrowser.xml
+++ b/browser/base/content/tabbrowser.xml
@@ -4525,17 +4525,17 @@
         let windowUtils = window.getInterface(Ci.nsIDOMWindowUtils);
         let scale = windowUtils.screenPixelsPerCSSPixel / windowUtils.fullZoom;
         let canvas = document.createElementNS("http://www.w3.org/1999/xhtml", "canvas");
         canvas.mozOpaque = true;
         canvas.width = 160 * scale;
         canvas.height = 90 * scale;
         if (!gMultiProcessBrowser) {
           // Bug 863512 - Make page thumbnails work in e10s
-          PageThumbs.captureToCanvas(browser, canvas);
+          PageThumbs.captureToCanvas(browser.contentWindow, canvas);
         }
         dt.setDragImage(canvas, -16 * scale, -16 * scale);
 
         // _dragData.offsetX/Y give the coordinates that the mouse should be
         // positioned relative to the corner of the new window created upon
         // dragend such that the mouse appears to have the same position
         // relative to the corner of the dragged tab.
         function clientX(ele) ele.getBoundingClientRect().left;

--- a/browser/components/tabview/tabitems.js
+++ b/browser/components/tabview/tabitems.js
@@ -1378,19 +1378,25 @@ TabCanvas.prototype = Utils.extend(new S
   // ----------
   // Function: paint
   paint: function TabCanvas_paint(evt) {
     var w = this.canvas.width;
     var h = this.canvas.height;
     if (!w || !h)
       return;
 
-    gPageThumbnails.captureToCanvas(this.tab.linkedBrowser, this.canvas, () => {
-      this._sendToSubscribers("painted");
-    });
+    if (!this.tab.linkedBrowser.contentWindow) {
+      Utils.log('no tab.linkedBrowser.contentWindow in TabCanvas.paint()');
+      return;
+    }
+
+    let win = this.tab.linkedBrowser.contentWindow;
+    gPageThumbnails.captureToCanvas(win, this.canvas);
+
+    this._sendToSubscribers("painted");
   },
 
   // ----------
   // Function: toImageData
   toImageData: function TabCanvas_toImageData() {
     return this.canvas.toDataURL("image/png");
   }
 });

deleted file mode 100644
--- a/toolkit/components/thumbnails/PageThumbUtils.jsm
+++ /dev/null
@@ -1,105 +0,0 @@
-/* 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/. */
-
-/*
- * Common thumbnailing routines used by various consumers, including
- * PageThumbs and backgroundPageThumbsContent.
- */
-
-this.EXPORTED_SYMBOLS = ["PageThumbUtils"];
-
-const { classes: Cc, interfaces: Ci, utils: Cu } = Components;
-
-Cu.import("resource://gre/modules/XPCOMUtils.jsm", this);
-Cu.import("resource://gre/modules/Services.jsm");
-Cu.import("resource://gre/modules/Promise.jsm", this);
-
-this.PageThumbUtils = {
-  // The default background color for page thumbnails.
-  THUMBNAIL_BG_COLOR: "#fff",
-  // The namespace for thumbnail canvas elements.
-  HTML_NAMESPACE: "http://www.w3.org/1999/xhtml",
-
-  /**
-   * Creates a new canvas element in the context of aWindow, or if aWindow
-   * is undefined, in the context of hiddenDOMWindow.
-   *
-   * @param aWindow (optional) The document of this window will be used to
-   *  create the canvas.  If not given, the hidden window will be used.
-   * @return The newly created canvas.
-   */
-  createCanvas: function (aWindow) {
-    let doc = (aWindow || Services.appShell.hiddenDOMWindow).document;
-    let canvas = doc.createElementNS(this.HTML_NAMESPACE, "canvas");
-    canvas.mozOpaque = true;
-    canvas.mozImageSmoothingEnabled = true;
-    let [thumbnailWidth, thumbnailHeight] = this.getThumbnailSize();
-    canvas.width = thumbnailWidth;
-    canvas.height = thumbnailHeight;
-    return canvas;
-  },
-
-  /**
-   * Calculates a preferred initial thumbnail size based on current desktop
-   * dimensions. The resulting dims will generally be about 1/3 the
-   * size of the desktop. (jimm: why??)
-   *
-   * @return The calculated thumbnail size or a default if unable to calculate.
-   */
-  getThumbnailSize: function () {
-    if (!this._thumbnailWidth || !this._thumbnailHeight) {
-      let screenManager = Cc["@mozilla.org/gfx/screenmanager;1"]
-                            .getService(Ci.nsIScreenManager);
-      let left = {}, top = {}, width = {}, height = {};
-      screenManager.primaryScreen.GetRectDisplayPix(left, top, width, height);
-      this._thumbnailWidth = Math.round(width.value / 3);
-      this._thumbnailHeight = Math.round(height.value / 3);
-    }
-    return [this._thumbnailWidth, this._thumbnailHeight];
-  },
-
-  /**
-   * Determine a good thumbnail crop size and scale for a given content
-   * window.
-   *
-   * @param aWindow The content window.
-   * @param aCanvas The target canvas.
-   * @return An array containing width, height and scale.
-   */
-  determineCropSize: function (aWindow, aCanvas) {
-    if (Cu.isCrossProcessWrapper(aWindow)) {
-      throw new Error('Do not pass cpows here.');
-    }
-    let utils = aWindow.QueryInterface(Ci.nsIInterfaceRequestor)
-                       .getInterface(Ci.nsIDOMWindowUtils);
-    // aWindow may be a cpow, add exposed props security values.
-    let sbWidth = {}, sbHeight = {};
-
-    try {
-      utils.getScrollbarSize(false, sbWidth, sbHeight);
-    } catch (e) {
-      // This might fail if the window does not have a presShell.
-      Cu.reportError("Unable to get scrollbar size in determineCropSize.");
-      sbWidth.value = sbHeight.value = 0;
-    }
-
-    // Even in RTL mode, scrollbars are always on the right.
-    // So there's no need to determine a left offset.
-    let width = aWindow.innerWidth - sbWidth.value;
-    let height = aWindow.innerHeight - sbHeight.value;
-
-    let {width: thumbnailWidth, height: thumbnailHeight} = aCanvas;
-    let scale = Math.min(Math.max(thumbnailWidth / width, thumbnailHeight / height), 1);
-    let scaledWidth = width * scale;
-    let scaledHeight = height * scale;
-
-    if (scaledHeight > thumbnailHeight)
-      height -= Math.floor(Math.abs(scaledHeight - thumbnailHeight) * scale);
-
-    if (scaledWidth > thumbnailWidth)
-      width -= Math.floor(Math.abs(scaledWidth - thumbnailWidth) * scale);
-
-    return [width, height, scale];
-  }
-};

--- a/toolkit/components/thumbnails/PageThumbs.jsm
+++ b/toolkit/components/thumbnails/PageThumbs.jsm
@@ -5,34 +5,38 @@
 "use strict";
 
 this.EXPORTED_SYMBOLS = ["PageThumbs", "PageThumbsStorage"];
 
 const Cu = Components.utils;
 const Cc = Components.classes;
 const Ci = Components.interfaces;
 
+const HTML_NAMESPACE = "http://www.w3.org/1999/xhtml";
 const PREF_STORAGE_VERSION = "browser.pagethumbnails.storage_version";
 const LATEST_STORAGE_VERSION = 3;
 
 const EXPIRATION_MIN_CHUNK_SIZE = 50;
 const EXPIRATION_INTERVAL_SECS = 3600;
 
-var gRemoteThumbId = 0;
-
 // If a request for a thumbnail comes in and we find one that is "stale"
 // (or don't find one at all) we automatically queue a request to generate a
 // new one.
 const MAX_THUMBNAIL_AGE_SECS = 172800; // 2 days == 60*60*24*2 == 172800 secs.
 
 /**
  * Name of the directory in the profile that contains the thumbnails.
  */
 const THUMBNAIL_DIRECTORY = "thumbnails";
 
+/**
+ * The default background color for page thumbnails.
+ */
+const THUMBNAIL_BG_COLOR = "#fff";
+
 Cu.import("resource://gre/modules/XPCOMUtils.jsm", this);
 Cu.import("resource://gre/modules/PromiseWorker.jsm", this);
 Cu.import("resource://gre/modules/Promise.jsm", this);
 Cu.import("resource://gre/modules/osfile.jsm", this);
 
 XPCOMUtils.defineLazyModuleGetter(this, "NetUtil",
   "resource://gre/modules/NetUtil.jsm");
 
@@ -60,18 +64,16 @@ XPCOMUtils.defineLazyGetter(this, "gUnic
 });
 
 XPCOMUtils.defineLazyModuleGetter(this, "Task",
   "resource://gre/modules/Task.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "Deprecated",
   "resource://gre/modules/Deprecated.jsm");
 XPCOMUtils.defineLazyModuleGetter(this, "AsyncShutdown",
   "resource://gre/modules/AsyncShutdown.jsm");
-XPCOMUtils.defineLazyModuleGetter(this, "PageThumbUtils",
-  "resource://gre/modules/PageThumbUtils.jsm");
 
 /**
  * Utilities for dealing with promises and Task.jsm
  */
 const TaskUtils = {
   /**
    * Read the bytes from a blob, asynchronously.
    *
@@ -161,195 +163,123 @@ this.PageThumbs = {
     * @param aUrl The web page's url.
     * @return The path of the thumbnail file.
     */
    getThumbnailPath: function PageThumbs_getThumbnailPath(aUrl) {
      return PageThumbsStorage.getFilePathForURL(aUrl);
    },
 
   /**
-   * Asynchronously returns a thumbnail as a blob for the given
-   * window.
+   * Captures a thumbnail for the given window.
+   * @param aWindow The DOM window to capture a thumbnail from.
+   * @param aCallback The function to be called when the thumbnail has been
+   *                  captured. The first argument will be the data stream
+   *                  containing the image data.
+   */
+  capture: function PageThumbs_capture(aWindow, aCallback) {
+    if (!this._prefEnabled()) {
+      return;
+    }
+
+    let canvas = this.createCanvas();
+    this.captureToCanvas(aWindow, canvas);
+
+    // Fetch the canvas data on the next event loop tick so that we allow
+    // some event processing in between drawing to the canvas and encoding
+    // its data. We want to block the UI as short as possible. See bug 744100.
+    Services.tm.currentThread.dispatch(function () {
+      canvas.mozFetchAsStream(aCallback, this.contentType);
+    }.bind(this), Ci.nsIThread.DISPATCH_NORMAL);
+  },
+
+
+  /**
+   * Captures a thumbnail for the given window.
    *
-   * @param aBrowser The <browser> to capture a thumbnail from.
+   * @param aWindow The DOM window to capture a thumbnail from.
    * @return {Promise}
    * @resolve {Blob} The thumbnail, as a Blob.
    */
-  captureToBlob: function PageThumbs_captureToBlob(aBrowser) {
+  captureToBlob: function PageThumbs_captureToBlob(aWindow) {
     if (!this._prefEnabled()) {
       return null;
     }
 
-    let deferred = Promise.defer();
+    let canvas = this.createCanvas();
+    this.captureToCanvas(aWindow, canvas);
 
-    let canvas = this.createCanvas();
-    this.captureToCanvas(aBrowser, canvas, () => {
-      canvas.toBlob(blob => {
-        deferred.resolve(blob, this.contentType);
-      });
+    let deferred = Promise.defer();
+    let type = this.contentType;
+    // Fetch the canvas data on the next event loop tick so that we allow
+    // some event processing in between drawing to the canvas and encoding
+    // its data. We want to block the UI as short as possible. See bug 744100.
+    canvas.toBlob(function asBlob(blob) {
+      deferred.resolve(blob, type);
     });
-
     return deferred.promise;
   },
 
   /**
    * Captures a thumbnail from a given window and draws it to the given canvas.
-   * Note, when dealing with remote content, this api draws into the passed
-   * canvas asynchronously. Pass aCallback to receive an async callback after
-   * canvas painting has completed.
-   * @param aBrowser The browser to capture a thumbnail from.
+   * @param aWindow The DOM window to capture a thumbnail from.
    * @param aCanvas The canvas to draw to.
-   * @param aCallback (optional) A callback invoked once the thumbnail has been
-   * rendered to aCanvas.
    */
-  captureToCanvas: function PageThumbs_captureToCanvas(aBrowser, aCanvas, aCallback) {
+  captureToCanvas: function PageThumbs_captureToCanvas(aWindow, aCanvas) {
     let telemetryCaptureTime = new Date();
-    this._captureToCanvas(aBrowser, aCanvas, function () {
-      Services.telemetry
-              .getHistogramById("FX_THUMBNAILS_CAPTURE_TIME_MS")
-              .add(new Date() - telemetryCaptureTime);
-      if (aCallback) {
-        aCallback(aCanvas);
-      }
-    });
+    this._captureToCanvas(aWindow, aCanvas);
+    let telemetry = Services.telemetry;
+    telemetry.getHistogramById("FX_THUMBNAILS_CAPTURE_TIME_MS")
+      .add(new Date() - telemetryCaptureTime);
   },
 
   // The background thumbnail service captures to canvas but doesn't want to
   // participate in this service's telemetry, which is why this method exists.
-  _captureToCanvas: function (aBrowser, aCanvas, aCallback) {
-    if (aBrowser.isRemoteBrowser) {
-      Task.spawn(function () {
-        let data =
-          yield this._captureRemoteThumbnail(aBrowser, aCanvas);
-        let canvas = data.thumbnail;
-        let ctx = canvas.getContext("2d");
-        let imgData = ctx.getImageData(0, 0, canvas.width, canvas.height);
-        aCanvas.getContext("2d").putImageData(imgData, 0, 0);
-        if (aCallback) {
-          aCallback(aCanvas);
-        }
-      }.bind(this));
-      return;
-    }
-
-    // Generate in-process content thumbnail
-    let [width, height, scale] =
-      PageThumbUtils.determineCropSize(aBrowser.contentWindow, aCanvas);
+  _captureToCanvas: function PageThumbs__captureToCanvas(aWindow, aCanvas) {
+    let [sw, sh, scale] = this._determineCropSize(aWindow, aCanvas);
     let ctx = aCanvas.getContext("2d");
 
     // Scale the canvas accordingly.
     ctx.save();
     ctx.scale(scale, scale);
 
     try {
       // Draw the window contents to the canvas.
-      ctx.drawWindow(aBrowser.contentWindow, 0, 0, width, height,
-                     PageThumbUtils.THUMBNAIL_BG_COLOR,
+      ctx.drawWindow(aWindow, 0, 0, sw, sh, THUMBNAIL_BG_COLOR,
                      ctx.DRAWWINDOW_DO_NOT_FLUSH);
     } catch (e) {
       // We couldn't draw to the canvas for some reason.
     }
+
     ctx.restore();
-
-    if (aCallback) {
-      aCallback(aCanvas);
-    }
   },
 
   /**
-   * Asynchrnously render an appropriately scaled thumbnail to canvas.
-   *
-   * @param aBrowser The browser to capture a thumbnail from.
-   * @param aCanvas The canvas to draw to.
-   * @return a promise
-   */
-  _captureRemoteThumbnail: function (aBrowser, aCanvas) {
-    let deferred = Promise.defer();
-
-    // The index we send with the request so we can identify the
-    // correct response.
-    let index = gRemoteThumbId++;
-
-    // Thumbnail request response handler
-    let mm = aBrowser.messageManager;
-
-    // Browser:Thumbnail:Response handler
-    let thumbFunc = function (aMsg) {
-      // Ignore events unrelated to our request
-      if (aMsg.data.id != index) {
-        return;
-      }
-
-      mm.removeMessageListener("Browser:Thumbnail:Response", thumbFunc);
-      let imageBlob = aMsg.data.thumbnail;
-      let doc = aBrowser.parentElement.ownerDocument;
-      let reader = Cc["@mozilla.org/files/filereader;1"].
-                   createInstance(Ci.nsIDOMFileReader);
-      reader.addEventListener("loadend", function() {
-        let image = doc.createElementNS(PageThumbUtils.HTML_NAMESPACE, "img");
-        image.onload = function () {
-          let thumbnail = doc.createElementNS(PageThumbUtils.HTML_NAMESPACE, "canvas");
-          thumbnail.width = image.naturalWidth;
-          thumbnail.height = image.naturalHeight;
-          let ctx = thumbnail.getContext("2d");
-          ctx.drawImage(image, 0, 0);
-          deferred.resolve({
-            thumbnail: thumbnail
-          });
-        }
-        image.src = reader.result;
-      });
-      // xxx wish there was a way to skip this encoding step
-      reader.readAsDataURL(imageBlob);
-    }
-
-    // Send a thumbnail request
-    mm.addMessageListener("Browser:Thumbnail:Response", thumbFunc);
-    mm.sendAsyncMessage("Browser:Thumbnail:Request", {
-      canvasWidth: aCanvas.width,
-      canvasHeight: aCanvas.height,
-      background: PageThumbUtils.THUMBNAIL_BG_COLOR,
-      id: index
-    });
-
-    return deferred.promise;
-  },
-
-  /**
    * Captures a thumbnail for the given browser and stores it to the cache.
    * @param aBrowser The browser to capture a thumbnail for.
    * @param aCallback The function to be called when finished (optional).
    */
   captureAndStore: function PageThumbs_captureAndStore(aBrowser, aCallback) {
     if (!this._prefEnabled()) {
       return;
     }
 
     let url = aBrowser.currentURI.spec;
-    let originalURL;
-    let channelError = false;
+    let channel = aBrowser.docShell.currentDocumentChannel;
+    let originalURL = channel.originalURI.spec;
 
-    if (!aBrowser.isRemoteBrowser) {
-      let channel = aBrowser.docShell.currentDocumentChannel;
-      originalURL = channel.originalURI.spec;
-      // see if this was an error response.
-      channelError = this._isChannelErrorResponse(channel);
-    } else {
-      // We need channel info (bug 1073957)
-      originalURL = url;
-    }
+    // see if this was an error response.
+    let wasError = this._isChannelErrorResponse(channel);
 
     Task.spawn((function task() {
       let isSuccess = true;
       try {
-        let blob = yield this.captureToBlob(aBrowser);
+        let blob = yield this.captureToBlob(aBrowser.contentWindow);
         let buffer = yield TaskUtils.readBlob(blob);
-        yield this._store(originalURL, url, buffer, channelError);
-      } catch (ex) {
-        Components.utils.reportError("Exception thrown during thumbnail capture: '" + ex + "'");
+        yield this._store(originalURL, url, buffer, wasError);
+      } catch (_) {
         isSuccess = false;
       }
       if (aCallback) {
         aCallback(isSuccess);
       }
     }).bind(this));
   },
 
@@ -440,23 +370,84 @@ this.PageThumbs = {
    * Unregister an expiration filter.
    * @param aFilter A filter that was previously passed to addExpirationFilter.
    */
   removeExpirationFilter: function PageThumbs_removeExpirationFilter(aFilter) {
     PageThumbsExpiration.removeFilter(aFilter);
   },
 
   /**
+   * Determines the crop size for a given content window.
+   * @param aWindow The content window.
+   * @param aCanvas The target canvas.
+   * @return An array containing width, height and scale.
+   */
+  _determineCropSize: function PageThumbs_determineCropSize(aWindow, aCanvas) {
+    let utils = aWindow.QueryInterface(Ci.nsIInterfaceRequestor)
+                       .getInterface(Ci.nsIDOMWindowUtils);
+    let sbWidth = {}, sbHeight = {};
+
+    try {
+      utils.getScrollbarSize(false, sbWidth, sbHeight);
+    } catch (e) {
+      // This might fail if the window does not have a presShell.
+      Cu.reportError("Unable to get scrollbar size in _determineCropSize.");
+      sbWidth.value = sbHeight.value = 0;
+    }
+
+    // Even in RTL mode, scrollbars are always on the right.
+    // So there's no need to determine a left offset.
+    let sw = aWindow.innerWidth - sbWidth.value;
+    let sh = aWindow.innerHeight - sbHeight.value;
+
+    let {width: thumbnailWidth, height: thumbnailHeight} = aCanvas;
+    let scale = Math.min(Math.max(thumbnailWidth / sw, thumbnailHeight / sh), 1);
+    let scaledWidth = sw * scale;
+    let scaledHeight = sh * scale;
+
+    if (scaledHeight > thumbnailHeight)
+      sh -= Math.floor(Math.abs(scaledHeight - thumbnailHeight) * scale);
+
+    if (scaledWidth > thumbnailWidth)
+      sw -= Math.floor(Math.abs(scaledWidth - thumbnailWidth) * scale);
+
+    return [sw, sh, scale];
+  },
+
+  /**
    * Creates a new hidden canvas element.
    * @param aWindow The document of this window will be used to create the
    *                canvas.  If not given, the hidden window will be used.
    * @return The newly created canvas.
    */
   createCanvas: function PageThumbs_createCanvas(aWindow) {
-    return PageThumbUtils.createCanvas(aWindow);
+    let doc = (aWindow || Services.appShell.hiddenDOMWindow).document;
+    let canvas = doc.createElementNS(HTML_NAMESPACE, "canvas");
+    canvas.mozOpaque = true;
+    canvas.mozImageSmoothingEnabled = true;
+    let [thumbnailWidth, thumbnailHeight] = this._getThumbnailSize();
+    canvas.width = thumbnailWidth;
+    canvas.height = thumbnailHeight;
+    return canvas;
+  },
+
+  /**
+   * Calculates the thumbnail size based on current desktop's dimensions.
+   * @return The calculated thumbnail size or a default if unable to calculate.
+   */
+  _getThumbnailSize: function PageThumbs_getThumbnailSize() {
+    if (!this._thumbnailWidth || !this._thumbnailHeight) {
+      let screenManager = Cc["@mozilla.org/gfx/screenmanager;1"]
+                            .getService(Ci.nsIScreenManager);
+      let left = {}, top = {}, width = {}, height = {};
+      screenManager.primaryScreen.GetRectDisplayPix(left, top, width, height);
+      this._thumbnailWidth = Math.round(width.value / 3);
+      this._thumbnailHeight = Math.round(height.value / 3);
+    }
+    return [this._thumbnailWidth, this._thumbnailHeight];
   },
 
   /**
    * Given a channel, returns true if it should be considered an "error
    * response", false otherwise.
    */
   _isChannelErrorResponse: function(channel) {
     // No valid document channel sounds like an error to me!

--- a/toolkit/components/thumbnails/content/backgroundPageThumbsContent.js
+++ b/toolkit/components/thumbnails/content/backgroundPageThumbsContent.js
@@ -1,17 +1,19 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+(function () { // bug 673569 workaround :(
+
 const { classes: Cc, interfaces: Ci, utils: Cu } = Components;
 
 Cu.importGlobalProperties(['Blob']);
 
-Cu.import("resource://gre/modules/PageThumbUtils.jsm");
+Cu.import("resource://gre/modules/PageThumbs.jsm");
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
 Cu.import("resource://gre/modules/Services.jsm");
 
 const STATE_LOADING = 1;
 const STATE_CAPTURING = 2;
 const STATE_CANCELED = 3;
 
 const backgroundPageThumbsContent = {
@@ -42,17 +44,17 @@ const backgroundPageThumbsContent = {
       addProgressListener(this, Ci.nsIWebProgress.NOTIFY_STATE_WINDOW);
   },
 
   observe: function (subj, topic, data) {
     // Arrange to prevent (most) popup dialogs for this window - popups done
     // in the parent (eg, auth) aren't prevented, but alert() etc are.
     // disableDialogs only works on the current inner window, so it has
     // to be called every page load, but before scripts run.
-    if (content && subj == content.document) {
+    if (subj == content.document) {
       content.
         QueryInterface(Ci.nsIInterfaceRequestor).
         getInterface(Ci.nsIDOMWindowUtils).
         disableDialogs();
     }
   },
 
   get _webNav() {
@@ -122,29 +124,19 @@ const backgroundPageThumbsContent = {
     }
   },
 
   _captureCurrentPage: function () {
     let capture = this._currentCapture;
     capture.finalURL = this._webNav.currentURI.spec;
     capture.pageLoadTime = new Date() - capture.pageLoadStartDate;
 
+    let canvas = PageThumbs.createCanvas(content);
     let canvasDrawDate = new Date();
-
-    let canvas = PageThumbUtils.createCanvas(content);
-    let [sw, sh, scale] = PageThumbUtils.determineCropSize(content, canvas);
-
-    let ctx = canvas.getContext("2d");
-    ctx.save();
-    ctx.scale(scale, scale);
-    ctx.drawWindow(content, 0, 0, sw, sh,
-                   PageThumbUtils.THUMBNAIL_BG_COLOR,
-                   ctx.DRAWWINDOW_DO_NOT_FLUSH);
-    ctx.restore();
-
+    PageThumbs._captureToCanvas(content, canvas);
     capture.canvasDrawTime = new Date() - canvasDrawDate;
 
     canvas.toBlob(blob => {
       capture.imageBlob = new Blob([blob]);
       // Load about:blank to finish the capture and wait for onStateChange.
       this._loadAboutBlank();
     });
   },
@@ -187,8 +179,10 @@ const backgroundPageThumbsContent = {
   QueryInterface: XPCOMUtils.generateQI([
     Ci.nsIWebProgressListener,
     Ci.nsISupportsWeakReference,
     Ci.nsIObserver,
   ]),
 };
 
 backgroundPageThumbsContent.init();
+
+})();

--- a/toolkit/components/thumbnails/moz.build
+++ b/toolkit/components/thumbnails/moz.build
@@ -10,12 +10,11 @@ EXTRA_COMPONENTS += [
     'BrowserPageThumbs.manifest',
     'PageThumbsProtocol.js',
 ]
 
 EXTRA_JS_MODULES += [
     'BackgroundPageThumbs.jsm',
     'PageThumbs.jsm',
     'PageThumbsWorker.js',
-    'PageThumbUtils.jsm',
 ]
 
 JAR_MANIFESTS += ['jar.mn']

--- a/toolkit/components/thumbnails/test/browser.ini
+++ b/toolkit/components/thumbnails/test/browser.ini
@@ -1,46 +1,40 @@
 [DEFAULT]
+skip-if = e10s # Bug 863512 - thumbnails are disabled with e10s enabled.
 support-files =
   background_red.html
   background_red_redirect.sjs
   background_red_scroll.html
   head.js
   privacy_cache_control.sjs
   thumbnails_background.sjs
   thumbnails_crash_content_helper.js
   thumbnails_update.sjs
 
 [browser_thumbnails_bg_bad_url.js]
 [browser_thumbnails_bg_crash_during_capture.js]
-skip-if = buildapp == 'mulet' || !crashreporter || e10s # crashing the remote thumbnailer crashes the remote test tab
+skip-if = buildapp == 'mulet' || !crashreporter
 [browser_thumbnails_bg_crash_while_idle.js]
-skip-if = buildapp == 'mulet' || !crashreporter || e10s
+skip-if = buildapp == 'mulet' || !crashreporter
 [browser_thumbnails_bg_basic.js]
 [browser_thumbnails_bg_queueing.js]
 [browser_thumbnails_bg_timeout.js]
 [browser_thumbnails_bg_redirect.js]
 [browser_thumbnails_bg_destroy_browser.js]
 [browser_thumbnails_bg_no_cookies_sent.js]
-skip-if = e10s # e10s cookie problems
 [browser_thumbnails_bg_no_cookies_stored.js]
 [browser_thumbnails_bg_no_auth_prompt.js]
 [browser_thumbnails_bg_no_alert.js]
 [browser_thumbnails_bg_no_duplicates.js]
 [browser_thumbnails_bg_captureIfMissing.js]
 [browser_thumbnails_bug726727.js]
 skip-if = buildapp == 'mulet'
 [browser_thumbnails_bug727765.js]
-skip-if = e10s # tries to open crypto/local file from the child
 [browser_thumbnails_bug818225.js]
-skip-if = (e10s && os == 'linux') # load event issues. see original bug for follow up.
 [browser_thumbnails_capture.js]
-skip-if = e10s # tries to call drawWindow with a remote browser.
 [browser_thumbnails_expiration.js]
 [browser_thumbnails_privacy.js]
-skip-if = e10s # nsSSLStatus has null mServerCert, bug 820466
 [browser_thumbnails_redirect.js]
-skip-if = e10s # bug 1050869
 [browser_thumbnails_storage.js]
 [browser_thumbnails_storage_migrate3.js]
 skip-if = buildapp == 'mulet'
 [browser_thumbnails_update.js]
-skip-if = e10s # tries to open crypto/local file from the child

--- a/toolkit/components/thumbnails/test/head.js
+++ b/toolkit/components/thumbnails/test/head.js
@@ -132,17 +132,16 @@ function captureAndCheckColor(aRed, aGre
       next();
     });
   });
 }
 
 /**
  * For a given URL, loads the corresponding thumbnail
  * to a canvas and passes its image data to the callback.
- * Note, not compat with e10s!
  * @param aURL The url associated with the thumbnail.
  * @param aCallback The function to pass the image data to.
  */
 function retrieveImageDataForURL(aURL, aCallback) {
   let width = 100, height = 100;
   let thumb = PageThumbs.getThumbnailURL(aURL, width, height);
   // create a tab with a chrome:// URL so it can host the thumbnail image.
   // Note that we tried creating the element directly in the top-level chrome

--- a/toolkit/content/browser-child.js
+++ b/toolkit/content/browser-child.js
@@ -6,19 +6,16 @@ let Cc = Components.classes;
 let Ci = Components.interfaces;
 let Cu = Components.utils;
 
 Cu.import("resource://gre/modules/Services.jsm");
 Cu.import('resource://gre/modules/XPCOMUtils.jsm');
 Cu.import("resource://gre/modules/RemoteAddonsChild.jsm");
 Cu.import("resource://gre/modules/Timer.jsm");
 
-XPCOMUtils.defineLazyModuleGetter(this, "PageThumbUtils",
-  "resource://gre/modules/PageThumbUtils.jsm");
-
 #ifdef MOZ_CRASHREPORTER
 XPCOMUtils.defineLazyServiceGetter(this, "CrashReporter",
                                    "@mozilla.org/xre/app-info;1",
                                    "nsICrashReporter");
 #endif
 
 let FocusSyncHandler = {
   init: function() {
@@ -366,47 +363,16 @@ addEventListener("ZoomChangeUsingMouseWh
   sendAsyncMessage("ZoomChangeUsingMouseWheel", {});
 }, false);
 
 addMessageListener("UpdateCharacterSet", function (aMessage) {
   docShell.charset = aMessage.data.value;
   docShell.gatherCharsetMenuTelemetry();
 });
 
-/**
- * Remote thumbnail request handler for PageThumbs thumbnails.
- */
-addMessageListener("Browser:Thumbnail:Request", function (aMessage) {
-  let thumbnail = content.document.createElementNS(PageThumbUtils.HTML_NAMESPACE,
-                                                   "canvas");
-  thumbnail.mozOpaque = true;
-  thumbnail.mozImageSmoothingEnabled = true;
-
-  thumbnail.width = aMessage.data.canvasWidth;
-  thumbnail.height = aMessage.data.canvasHeight;
-
-  let [width, height, scale] =
-    PageThumbUtils.determineCropSize(content, thumbnail);
-
-  let ctx = thumbnail.getContext("2d");
-  ctx.save();
-  ctx.scale(scale, scale);
-  ctx.drawWindow(content, 0, 0, width, height,
-                 aMessage.data.background,
-                 ctx.DRAWWINDOW_DO_NOT_FLUSH);
-  ctx.restore();
-
-  thumbnail.toBlob(function (aBlob) {
-    sendAsyncMessage("Browser:Thumbnail:Response", {
-      thumbnail: aBlob,
-      id: aMessage.data.id
-    });
-  });
-});
-
 // The AddonsChild needs to be rooted so that it stays alive as long as
 // the tab.
 let AddonsChild;
 if (Services.appinfo.browserTabsRemoteAutostart) {
   // Currently, the addon shims are only supported when autostarting
   // with remote tabs.
   AddonsChild = RemoteAddonsChild.init(this);