Introduce separate client and init path for single-threaded cc

cc/test/fake_layer_tree_host.h

Index: cc/test/fake_layer_tree_host.h
diff --git a/cc/test/fake_layer_tree_host.h b/cc/test/fake_layer_tree_host.h
index 3acfdd291ee53cb81c6bfc5ac677f06546a56f5b..09657ef68d1144191ee3fcecfbe991f8018b5be7 100644
--- a/cc/test/fake_layer_tree_host.h
+++ b/cc/test/fake_layer_tree_host.h
@@ -14,7 +14,7 @@
 
 namespace cc {
 
-class FakeLayerTreeHost : protected LayerTreeHost {
+class FakeLayerTreeHost : public LayerTreeHost {
  public:
   static scoped_ptr<FakeLayerTreeHost> Create();
 
@@ -36,6 +36,7 @@ class FakeLayerTreeHost : protected LayerTreeHost {
 
   using LayerTreeHost::ScheduleMicroBenchmark;
   using LayerTreeHost::SetOutputSurfaceLostForTesting;
+  using LayerTreeHost::InitializeSingleThreaded;
   using LayerTreeHost::InitializeForTesting;
   void UpdateLayers(ResourceUpdateQueue* queue) {
     LayerTreeHost::UpdateLayers(queue);