Rename RootWindowHost* to WindowTreeHost*

ash/test/test_metro_viewer_process_host.cc

Index: ash/test/test_metro_viewer_process_host.cc
diff --git a/ash/test/test_metro_viewer_process_host.cc b/ash/test/test_metro_viewer_process_host.cc
index 4af0c5807d3812549e9e440c860c0fa32b0a779a..9dc3406e65cfc56a77568e791234ca0a92dbd888 100644
--- a/ash/test/test_metro_viewer_process_host.cc
+++ b/ash/test/test_metro_viewer_process_host.cc
@@ -23,14 +23,14 @@ TestMetroViewerProcessHost::~TestMetroViewerProcessHost() {
 
 void TestMetroViewerProcessHost::OnChannelError() {
   closed_unexpectedly_ = true;
-  aura::RemoteRootWindowHostWin::Instance()->Disconnected();
+  aura::RemoteWindowTreeHostWin::Instance()->Disconnected();
 }
 
 void TestMetroViewerProcessHost::OnSetTargetSurface(
     gfx::NativeViewId target_surface) {
   DLOG(INFO) << __FUNCTION__ << ", target_surface = " << target_surface;
   HWND hwnd = reinterpret_cast<HWND>(target_surface);
-  aura::RemoteRootWindowHostWin::Instance()->Connected(this, hwnd);
+  aura::RemoteWindowTreeHostWin::Instance()->Connected(this, hwnd);
 
   backing_surface_.reset(new AcceleratedSurface(hwnd));
 }