respect --force-compositing-mode for chrome: pages

content/browser/tab_contents/tab_contents.cc

 // Copyright (c) 2011 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/browser/tab_contents/tab_contents.h"
 
 #include <cmath>
 
 #include "base/command_line.h"
 #include "base/metrics/histogram.h"
@@ skipping 1674 matching lines @@
       message,
       reply_msg);
 }
 
 WebPreferences TabContents::GetWebkitPrefs() {
   WebPreferences web_prefs =
       content::GetContentClient()->browser()->GetWebkitPrefs(
           render_view_host()->process()->browser_context(), false);
 
   // Force accelerated compositing and 2d canvas off for chrome:, about: and
-  // chrome-devtools: pages.
-  if (GetURL().SchemeIs(chrome::kChromeDevToolsScheme) ||
+  // chrome-devtools: pages (unless it's specifically allowed).
+  if ((GetURL().SchemeIs(chrome::kChromeDevToolsScheme) ||
       GetURL().SchemeIs(chrome::kChromeUIScheme) ||
-      GetURL().SchemeIs(chrome::kAboutScheme)) {
+      GetURL().SchemeIs(chrome::kAboutScheme)) &&
+      !web_prefs.allow_webui_compositing) {
     web_prefs.accelerated_compositing_enabled = false;
     web_prefs.accelerated_2d_canvas_enabled = false;
   }
 
 #if defined(OS_MACOSX)
   // Disable accelerated compositing if IOSurface's are not supported,
   // as is the case in 10.5.
   if (!IOSurfaceSupport::Initialize())
       web_prefs.accelerated_compositing_enabled = false;
 #endif
@@ skipping 170 matching lines @@
 }
 
 void TabContents::SwapInRenderViewHost(RenderViewHost* rvh) {
   render_manager_.SwapInRenderViewHost(rvh);
 }
 
 void TabContents::CreateViewAndSetSizeForRVH(RenderViewHost* rvh) {
   RenderWidgetHostView* rwh_view = view()->CreateViewForWidget(rvh);
   rwh_view->SetSize(view()->GetContainerSize());
 }