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

cc/test/layer_tree_test.cc

 // Copyright 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 "cc/test/layer_tree_test.h"
 
 #include "base/command_line.h"
 #include "cc/animation/animation.h"
 #include "cc/animation/animation_registrar.h"
 #include "cc/animation/layer_animation_controller.h"
@@ skipping 233 matching lines @@
 
   virtual void Layout() OVERRIDE {
     test_hooks_->Layout();
   }
 
   virtual void ApplyScrollAndScale(gfx::Vector2d scroll_delta,
                                    float scale) OVERRIDE {
     test_hooks_->ApplyScrollAndScale(scroll_delta, scale);
   }
 
-  virtual scoped_ptr<OutputSurface> CreateOutputSurface() OVERRIDE {
+  virtual scoped_ptr<OutputSurface> CreateOutputSurface(bool fallback)
+      OVERRIDE {
     return test_hooks_->CreateOutputSurface();
   }
 
   virtual void DidInitializeOutputSurface(bool succeeded) OVERRIDE {
     test_hooks_->DidInitializeOutputSurface(succeeded);
   }
 
   virtual void DidFailToInitializeOutputSurface() OVERRIDE {
     test_hooks_->DidFailToInitializeOutputSurface();
   }
@@ skipping 358 matching lines @@
 
 scoped_refptr<cc::ContextProvider> LayerTreeTest::
     OffscreenContextProviderForCompositorThread() {
   if (!compositor_thread_contexts_.get() ||
       compositor_thread_contexts_->DestroyedOnMainThread())
     compositor_thread_contexts_ = FakeContextProvider::Create();
   return compositor_thread_contexts_;
 }
 
 }  // namespace cc