Renames aura::client::WindowTreeClient to WindowParentingClient

blimp/engine/session/blimp_engine_session.h

Index: blimp/engine/session/blimp_engine_session.h
diff --git a/blimp/engine/session/blimp_engine_session.h b/blimp/engine/session/blimp_engine_session.h
index aa65afde1009ae75be579a3e18e6634efdf7b73d..f815a5a4102bbea8adf17761084503447995292e 100644
--- a/blimp/engine/session/blimp_engine_session.h
+++ b/blimp/engine/session/blimp_engine_session.h
@@ -30,7 +30,7 @@ class WindowTreeHost;
 
 namespace client {
 class DefaultCaptureClient;
-class WindowTreeClient;
+class WindowParentingClient;
 }  // namespace client
 }  // namespace aura
 
@@ -177,7 +177,7 @@ class BlimpEngineSession : public BlimpMessageProcessor,
   std::unique_ptr<aura::client::DefaultCaptureClient> capture_client_;
 
   // Used to attach null-parented windows (e.g. popups) to the root window.
-  std::unique_ptr<aura::client::WindowTreeClient> window_tree_client_;
+  std::unique_ptr<aura::client::WindowParentingClient> window_parenting_client_;
 
   // Manages all global settings for the engine session.
   SettingsManager* settings_manager_;