Fall back to software mode if Aura can't create a GL context

ui/compositor/test/test_context_factory.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 "ui/compositor/test/test_context_factory.h"
 
 #include "cc/output/output_surface.h"
 #include "cc/test/test_context_provider.h"
 #include "ui/compositor/reflector.h"
 
 namespace ui {
 
 TestContextFactory::TestContextFactory() {}
 
 TestContextFactory::~TestContextFactory() {}
 
 scoped_ptr<cc::OutputSurface> TestContextFactory::CreateOutputSurface(
-    Compositor* compositor) {
+    Compositor* compositor, bool software_fallback) {
+  DCHECK(!software_fallback);
   return make_scoped_ptr(
       new cc::OutputSurface(cc::TestContextProvider::Create()));
 }
 
 scoped_refptr<Reflector> TestContextFactory::CreateReflector(
     Compositor* mirrored_compositor,
     Layer* mirroring_layer) {
   return new Reflector();
 }
 
@@ skipping 27 matching lines @@
 
   return shared_main_thread_contexts_;
 }
 
 void TestContextFactory::RemoveCompositor(Compositor* compositor) {
 }
 
 bool TestContextFactory::DoesCreateTestContexts() { return true; }
 
 }  // namespace ui