Add a flag to allow renderer to use software compositor when GL compositor doesn't work.

webkit/support/web_layer_tree_view_impl_for_testing.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 "webkit/support/web_layer_tree_view_impl_for_testing.h"
 
 #include "base/command_line.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/synchronization/lock.h"
 #include "cc/base/switches.h"
@@ skipping 140 matching lines @@
 void WebLayerTreeViewImplForTesting::renderingStats(WebRenderingStats&) const {}
 
 void WebLayerTreeViewImplForTesting::Layout() {
 }
 
 void WebLayerTreeViewImplForTesting::ApplyScrollAndScale(
     gfx::Vector2d scroll_delta,
     float page_scale) {}
 
 scoped_ptr<cc::OutputSurface>
-WebLayerTreeViewImplForTesting::CreateOutputSurface() {
+WebLayerTreeViewImplForTesting::CreateOutputSurface(bool fallback) {
   scoped_ptr<cc::OutputSurface> surface;
   scoped_ptr<WebGraphicsContext3D> context3d(
       new cc::FakeWebGraphicsContext3D);
   surface.reset(new cc::OutputSurface(context3d.Pass()));
   return surface.Pass();
 }
 
 void WebLayerTreeViewImplForTesting::ScheduleComposite() {
 }
 
 scoped_refptr<cc::ContextProvider>
 WebLayerTreeViewImplForTesting::OffscreenContextProviderForMainThread() {
   return webkit::gpu::TestContextProviderFactory::GetInstance()->
       OffscreenContextProviderForMainThread();
 }
 
 scoped_refptr<cc::ContextProvider>
 WebLayerTreeViewImplForTesting::OffscreenContextProviderForCompositorThread() {
   return webkit::gpu::TestContextProviderFactory::GetInstance()->
       OffscreenContextProviderForCompositorThread();
 }
 
 }  // namespace webkit