Rename StackingClient -> WindowTreeClient

ui/aura/test/aura_test_helper.h

Index: ui/aura/test/aura_test_helper.h
diff --git a/ui/aura/test/aura_test_helper.h b/ui/aura/test/aura_test_helper.h
index 02f9c31a8d2e7e45d353b37288df9d7644efc970..27cd44219f082d18fc1dae5ac998b6453cc5ec5f 100644
--- a/ui/aura/test/aura_test_helper.h
+++ b/ui/aura/test/aura_test_helper.h
@@ -30,7 +30,7 @@ class DefaultCaptureClient;
 class FocusClient;
 }
 namespace test {
-class TestStackingClient;
+class TestWindowTreeClient;
 
 // A helper class owned by tests that does common initialization required for
 // Aura use. This class creates a root window with clients and other objects
@@ -60,7 +60,7 @@ class AuraTestHelper {
   bool teardown_called_;
   bool owns_root_window_;
   scoped_ptr<RootWindow> root_window_;
-  scoped_ptr<TestStackingClient> stacking_client_;
+  scoped_ptr<TestWindowTreeClient> stacking_client_;
   scoped_ptr<client::DefaultActivationClient> activation_client_;
   scoped_ptr<client::DefaultCaptureClient> capture_client_;
   scoped_ptr<ui::InputMethod> test_input_method_;