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

content/renderer/gpu/render_widget_compositor.cc

 // Copyright (c) 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/renderer/gpu/render_widget_compositor.h"
 
 #include <limits>
 #include <string>
 
 #include "base/command_line.h"
@@ skipping 519 matching lines @@
 
 void RenderWidgetCompositor::Layout() {
   widget_->webwidget()->layout();
 }
 
 void RenderWidgetCompositor::ApplyScrollAndScale(gfx::Vector2d scroll_delta,
                                                  float page_scale) {
   widget_->webwidget()->applyScrollAndScale(scroll_delta, page_scale);
 }
 
-scoped_ptr<cc::OutputSurface> RenderWidgetCompositor::CreateOutputSurface() {
-  return widget_->CreateOutputSurface();
+scoped_ptr<cc::OutputSurface> RenderWidgetCompositor::CreateOutputSurface(
+    bool fallback) {
+  return widget_->CreateOutputSurface(fallback);
 }
 
 void RenderWidgetCompositor::DidInitializeOutputSurface(bool success) {
   if (!success)
     widget_->webwidget()->didExitCompositingMode();
 }
 
 void RenderWidgetCompositor::WillCommit() {
   widget_->InstrumentWillComposite();
 }
@@ skipping 21 matching lines @@
   return RenderThreadImpl::current()->OffscreenContextProviderForMainThread();
 }
 
 scoped_refptr<cc::ContextProvider>
 RenderWidgetCompositor::OffscreenContextProviderForCompositorThread() {
   return RenderThreadImpl::current()->
       OffscreenContextProviderForCompositorThread();
 }
 
 }  // namespace content