Introduce separate client and init path for single-threaded cc

cc/test/fake_layer_tree_host_client.h

Index: cc/test/fake_layer_tree_host_client.h
diff --git a/cc/test/fake_layer_tree_host_client.h b/cc/test/fake_layer_tree_host_client.h
index 0bad7ad66027c4eef1bb7ec58af33f5af8d98d80..8b60f50659e1d9236a1e6a1af82600fab8980d34 100644
--- a/cc/test/fake_layer_tree_host_client.h
+++ b/cc/test/fake_layer_tree_host_client.h
@@ -8,12 +8,14 @@
 #include "base/memory/scoped_ptr.h"
 #include "cc/input/input_handler.h"
 #include "cc/test/test_context_provider.h"
-#include "cc/trees/layer_tree_host.h"
+#include "cc/trees/layer_tree_host_client.h"
+#include "cc/trees/layer_tree_host_single_thread_client.h"
 
 namespace cc {
 class OutputSurface;
 
-class FakeLayerTreeHostClient : public LayerTreeHostClient {
+class FakeLayerTreeHostClient : public LayerTreeHostClient,
+                                public LayerTreeHostSingleThreadClient {
  public:
   enum RendererOptions {
     DIRECT_3D,
@@ -24,6 +26,7 @@ class FakeLayerTreeHostClient : public LayerTreeHostClient {
   explicit FakeLayerTreeHostClient(RendererOptions options);
   virtual ~FakeLayerTreeHostClient();
 
+  // LayerTreeHostClient implementation.
   virtual void WillBeginMainFrame() OVERRIDE {}
   virtual void DidBeginMainFrame() OVERRIDE {}
   virtual void Animate(double frame_begin_time) OVERRIDE {}
@@ -37,11 +40,12 @@ class FakeLayerTreeHostClient : public LayerTreeHostClient {
   virtual void DidCommit() OVERRIDE {}
   virtual void DidCommitAndDrawFrame() OVERRIDE {}
   virtual void DidCompleteSwapBuffers() OVERRIDE {}
+  virtual scoped_refptr<ContextProvider> OffscreenContextProvider() OVERRIDE;
 
-  // Used only in the single-threaded path.
+  // LayerTreeHostSingleThreadClient implementation.
   virtual void ScheduleComposite() OVERRIDE {}
-
-  virtual scoped_refptr<ContextProvider> OffscreenContextProvider() OVERRIDE;
+  virtual void DidPostSwapBuffers() OVERRIDE {}
+  virtual void DidAbortSwapBuffers() OVERRIDE {}
 
  private:
   bool use_software_rendering_;