Introduce separate client and init path for single-threaded cc

cc/trees/layer_tree_host_unittest.cc

Index: cc/trees/layer_tree_host_unittest.cc
diff --git a/cc/trees/layer_tree_host_unittest.cc b/cc/trees/layer_tree_host_unittest.cc
index 59bad2e0db5ae2b0d53f1aab4de30251a240bf69..99c248247c7c5860b3829cbf754508866d49cc94 100644
--- a/cc/trees/layer_tree_host_unittest.cc
+++ b/cc/trees/layer_tree_host_unittest.cc
@@ -2373,7 +2373,7 @@ TEST(LayerTreeHostTest, PartialUpdatesWithGLRenderer) {
   settings.max_partial_texture_updates = 4;
 
   scoped_ptr<LayerTreeHost> host =
-      LayerTreeHost::Create(&client, NULL, settings, NULL);
+      LayerTreeHost::CreateSingleThreaded(&client, &client, NULL, settings);
   EXPECT_TRUE(host->InitializeOutputSurfaceIfNeeded());
   EXPECT_EQ(4u, host->settings().max_partial_texture_updates);
 }
@@ -2385,7 +2385,7 @@ TEST(LayerTreeHostTest, PartialUpdatesWithSoftwareRenderer) {
   settings.max_partial_texture_updates = 4;
 
   scoped_ptr<LayerTreeHost> host =
-      LayerTreeHost::Create(&client, NULL, settings, NULL);
+      LayerTreeHost::CreateSingleThreaded(&client, &client, NULL, settings);
   EXPECT_TRUE(host->InitializeOutputSurfaceIfNeeded());
   EXPECT_EQ(4u, host->settings().max_partial_texture_updates);
 }
@@ -2397,7 +2397,7 @@ TEST(LayerTreeHostTest, PartialUpdatesWithDelegatingRendererAndGLContent) {
   settings.max_partial_texture_updates = 4;
 
   scoped_ptr<LayerTreeHost> host =
-      LayerTreeHost::Create(&client, NULL, settings, NULL);
+      LayerTreeHost::CreateSingleThreaded(&client, &client, NULL, settings);
   EXPECT_TRUE(host->InitializeOutputSurfaceIfNeeded());
   EXPECT_EQ(0u, host->MaxPartialTextureUpdates());
 }
@@ -2410,7 +2410,7 @@ TEST(LayerTreeHostTest,
   settings.max_partial_texture_updates = 4;
 
   scoped_ptr<LayerTreeHost> host =
-      LayerTreeHost::Create(&client, NULL, settings, NULL);
+      LayerTreeHost::CreateSingleThreaded(&client, &client, NULL, settings);
   EXPECT_TRUE(host->InitializeOutputSurfaceIfNeeded());
   EXPECT_EQ(0u, host->MaxPartialTextureUpdates());
 }