cc: Make PrepareToDraw return an enum for why it aborts

cc/test/fake_layer_tree_host_impl.cc

 // Copyright 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.
 
 #include "cc/test/fake_layer_tree_host_impl.h"
 #include "cc/trees/layer_tree_impl.h"
 
 namespace cc {
 
 FakeLayerTreeHostImpl::FakeLayerTreeHostImpl(Proxy* proxy)
     : LayerTreeHostImpl(LayerTreeSettings(),
                         &client_,
                         proxy,
                         &stats_instrumentation_,
                         NULL,
                         0) {
   // Explicitly clear all debug settings.
   SetDebugState(LayerTreeDebugState());
+  SetViewportSize(gfx::Size(100, 100));
 }
 
 FakeLayerTreeHostImpl::FakeLayerTreeHostImpl(const LayerTreeSettings& settings,
                                              Proxy* proxy)
     : LayerTreeHostImpl(settings,
                         &client_,
                         proxy,
                         &stats_instrumentation_,
                         NULL,
                         0) {
@@ skipping 15 matching lines @@
     return LayerTreeHostImpl::CurrentFrameTimeTicks();
   return current_frame_time_ticks_;
 }
 
 void FakeLayerTreeHostImpl::SetCurrentFrameTimeTicks(
     base::TimeTicks current_frame_time_ticks) {
   current_frame_time_ticks_ = current_frame_time_ticks;
 }
 
 }  // namespace cc