cc: Add testing stubs for proxy test

cc/test/layer_tree_test.h

Index: cc/test/layer_tree_test.h
diff --git a/cc/test/layer_tree_test.h b/cc/test/layer_tree_test.h
index e7d618badaeef5d84df7f1a16c6d937472103db0..a8190f91f88178f7447a050bfa732b757753ceb3 100644
--- a/cc/test/layer_tree_test.h
+++ b/cc/test/layer_tree_test.h
@@ -10,6 +10,7 @@
 #include "cc/animation/animation_delegate.h"
 #include "cc/trees/layer_tree_host.h"
 #include "cc/trees/layer_tree_host_impl.h"
+#include "cc/trees/thread_proxy.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace Webkit {
@@ -178,6 +179,9 @@ class LayerTreeTest : public testing::Test, public TestHooks {
   FakeOutputSurface* output_surface() { return output_surface_; }
   int LastCommittedSourceFrameNumber(LayerTreeHostImpl* impl) const;
 
+  const ThreadProxy::MainThreadOnly& ThreadProxyMainOnly() const;
+  const ThreadProxy::CompositorThreadOnly& ThreadProxyImplOnly() const;
+
   void DestroyLayerTreeHost();
 
   // Override this for pixel tests, where you need a real output surface.