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

ui/compositor/compositor.h

 // 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.
 
 #ifndef UI_COMPOSITOR_COMPOSITOR_H_
 #define UI_COMPOSITOR_COMPOSITOR_H_
 
 #include <string>
 
 #include "base/containers/hash_tables.h"
@@ skipping 68 matching lines @@
 
   // Sets the global instance. Caller keeps ownership.
   // If this function isn't called (for tests), a "default" factory will be
   // created on the first call of GetInstance.
   static void SetInstance(ContextFactory* instance);
 
   // Creates an output surface for the given compositor. The factory may keep
   // per-compositor data (e.g. a shared context), that needs to be cleaned up
   // by calling RemoveCompositor when the compositor gets destroyed.
   virtual scoped_ptr<cc::OutputSurface> CreateOutputSurface(
-      Compositor* compositor) = 0;
+      Compositor* compositor, bool software_fallback) = 0;
 
   // Creates a reflector that copies the content of the |mirrored_compositor|
   // onto |mirroing_layer|.
   virtual scoped_refptr<Reflector> CreateReflector(
       Compositor* mirrored_compositor,
       Layer* mirroring_layer) = 0;
   // Removes the reflector, which stops the mirroring.
   virtual void RemoveReflector(scoped_refptr<Reflector> reflector) = 0;
 
   // Returns a reference to the offscreen context provider used by the
@@ skipping 288 matching lines @@
   bool draw_on_compositing_end_;
 
   base::WeakPtrFactory<Compositor> schedule_draw_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(Compositor);
 };
 
 }  // namespace ui
 
 #endif  // UI_COMPOSITOR_COMPOSITOR_H_