cc: Split Proxy to eliminate unnecessary dependencies on the impl side

cc/test/fake_layer_tree_host_impl.h

Index: cc/test/fake_layer_tree_host_impl.h
diff --git a/cc/test/fake_layer_tree_host_impl.h b/cc/test/fake_layer_tree_host_impl.h
index f47a098dd2f8b2a0fc4f66e289e1e977409559df..5114df5b37942b39a5c6f269cd645fb4f0bdb4ea 100644
--- a/cc/test/fake_layer_tree_host_impl.h
+++ b/cc/test/fake_layer_tree_host_impl.h
@@ -18,15 +18,15 @@ namespace cc {
 
 class FakeLayerTreeHostImpl : public LayerTreeHostImpl {
  public:
-  FakeLayerTreeHostImpl(Proxy* proxy,
+  FakeLayerTreeHostImpl(ThreadVerifier* thread_verifier,
                         SharedBitmapManager* manager,
                         TaskGraphRunner* task_graph_runner);
   FakeLayerTreeHostImpl(const LayerTreeSettings& settings,
-                        Proxy* proxy,
+                        ThreadVerifier* thread_verifier,
                         SharedBitmapManager* manager,
                         TaskGraphRunner* task_graph_runner);
   FakeLayerTreeHostImpl(const LayerTreeSettings& settings,
-                        Proxy* proxy,
+                        ThreadVerifier* thread_verifier,
                         SharedBitmapManager* manager,
                         TaskGraphRunner* task_graph_runner,
                         gpu::GpuMemoryBufferManager* gpu_memory_buffer_manager);