Introduce separate client and init path for single-threaded cc

cc/layers/ui_resource_layer_unittest.cc

Index: cc/layers/ui_resource_layer_unittest.cc
diff --git a/cc/layers/ui_resource_layer_unittest.cc b/cc/layers/ui_resource_layer_unittest.cc
index a2c75c16d041f06f66f92346eae310394d5d83d0..48dbdf58f710b3a3f0d2d43d16895b7b609bef02 100644
--- a/cc/layers/ui_resource_layer_unittest.cc
+++ b/cc/layers/ui_resource_layer_unittest.cc
@@ -10,6 +10,7 @@
 #include "cc/resources/resource_update_queue.h"
 #include "cc/resources/scoped_ui_resource.h"
 #include "cc/scheduler/texture_uploader.h"
+#include "cc/test/fake_layer_tree_host.h"
 #include "cc/test/fake_layer_tree_host_client.h"
 #include "cc/test/fake_output_surface.h"
 #include "cc/test/fake_output_surface_client.h"
@@ -29,30 +30,21 @@ using ::testing::AnyNumber;
 namespace cc {
 namespace {
 
-class MockLayerTreeHost : public LayerTreeHost {
- public:
-  explicit MockLayerTreeHost(LayerTreeHostClient* client)
-      : LayerTreeHost(client, NULL, LayerTreeSettings()) {
-    Initialize(NULL);
-  }
-};
-
 class UIResourceLayerTest : public testing::Test {
  public:
   UIResourceLayerTest() : fake_client_(FakeLayerTreeHostClient::DIRECT_3D) {}
 
-  cc::Proxy* Proxy() const { return layer_tree_host_->proxy(); }
-
  protected:
   virtual void SetUp() {
-    layer_tree_host_.reset(new MockLayerTreeHost(&fake_client_));
+    layer_tree_host_ = FakeLayerTreeHost::Create();
+    layer_tree_host_->InitializeSingleThreaded(&fake_client_);
   }
 
   virtual void TearDown() {
     Mock::VerifyAndClearExpectations(layer_tree_host_.get());
   }
 
-  scoped_ptr<MockLayerTreeHost> layer_tree_host_;
+  scoped_ptr<FakeLayerTreeHost> layer_tree_host_;
   FakeLayerTreeHostClient fake_client_;
 };