Don't trigger accelerated compositing for 3D CSS when using SwiftShader

content/browser/tab_contents/tab_contents.cc

 // Copyright (c) 2012 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 413 matching lines @@
     if (blacklist_type & content::GPU_FEATURE_TYPE_ACCELERATED_COMPOSITING)
       prefs.accelerated_compositing_enabled = false;
     if (blacklist_type & content::GPU_FEATURE_TYPE_WEBGL)
       prefs.experimental_webgl_enabled = false;
     if (blacklist_type & content::GPU_FEATURE_TYPE_ACCELERATED_2D_CANVAS)
       prefs.accelerated_2d_canvas_enabled = false;
     if (blacklist_type & content::GPU_FEATURE_TYPE_MULTISAMPLING)
       prefs.gl_multisampling_enabled = false;
 
     // Accelerated video and animation are slower than regular when using a
-    // software 3d rasterizer.
+    // software 3d rasterizer. 3D CSS may also be too slow to be worthwhile.
     if (gpu_data_manager->ShouldUseSoftwareRendering()) {
       prefs.accelerated_video_enabled = false;
       prefs.accelerated_animation_enabled = false;
+      prefs.accelerated_layers_enabled = false;
     }
   }
 
   if (ChildProcessSecurityPolicyImpl::GetInstance()->HasWebUIBindings(
           rvh->process()->GetID())) {
     prefs.loads_images_automatically = true;
     prefs.javascript_enabled = true;
   }
 
   prefs.is_online = !net::NetworkChangeNotifier::IsOffline();
@@ skipping 2023 matching lines @@
                    save_info,
                    this);
 }
 
 void TabContents::CreateViewAndSetSizeForRVH(RenderViewHost* rvh) {
   RenderWidgetHostView* rwh_view = GetView()->CreateViewForWidget(rvh);
   // Can be NULL during tests.
   if (rwh_view)
     rwh_view->SetSize(GetView()->GetContainerSize());
 }