Add chromium side flag for enabling/disabling layer squashing.

content/renderer/web_preferences.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/public/renderer/web_preferences.h"
 
 #include "base/strings/utf_string_conversions.h"
 #include "third_party/WebKit/public/platform/WebString.h"
 #include "third_party/WebKit/public/platform/WebURL.h"
 #include "third_party/WebKit/public/web/WebKit.h"
@@ skipping 194 matching lines @@
   settings->setAcceleratedCompositingForScrollableFramesEnabled(
       prefs.accelerated_compositing_for_scrollable_frames_enabled);
 
   // Enables composited scrolling for frames if requested on command line.
   settings->setCompositedScrollingForFramesEnabled(
       prefs.composited_scrolling_for_frames_enabled);
 
   // Uses the mock theme engine for scrollbars.
   settings->setMockScrollbarsEnabled(prefs.mock_scrollbars_enabled);
 
+  settings->setLayerSquashingEnabled(prefs.layer_squashing_enabled);
+
   settings->setThreadedHTMLParser(prefs.threaded_html_parser);
 
   // Display visualization of what has changed on the screen using an
   // overlay of rects, if requested on the command line.
   settings->setShowPaintRects(prefs.show_paint_rects);
 
   // Enable gpu-accelerated compositing if requested on the command line.
   settings->setAcceleratedCompositingEnabled(
       prefs.accelerated_compositing_enabled);
 
@@ skipping 143 matching lines @@
   settings->setPinchVirtualViewportEnabled(
       prefs.pinch_virtual_viewport_enabled);
 
   settings->setPinchOverlayScrollbarThickness(
       prefs.pinch_overlay_scrollbar_thickness);
   settings->setUseSolidColorScrollbars(prefs.use_solid_color_scrollbars);
   settings->setCompositorTouchHitTesting(prefs.compositor_touch_hit_testing);
 }
 
 }  // namespace content