Move root_window_host* in aura to window_tree_host*.

ui/aura/window_tree_host_win.h

Index: ui/aura/window_tree_host_win.h
diff --git a/ui/aura/root_window_host_win.h b/ui/aura/window_tree_host_win.h
similarity index 96%
rename from ui/aura/root_window_host_win.h
rename to ui/aura/window_tree_host_win.h
index 96f3e358103301a42febf86f0daa5e52848d7272..86976f5b9a1b973ad5659e914ca454ba1093bc1f 100644
--- a/ui/aura/root_window_host_win.h
+++ b/ui/aura/window_tree_host_win.h
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef UI_AURA_ROOT_WINDOW_HOST_WIN_H_
-#define UI_AURA_ROOT_WINDOW_HOST_WIN_H_
+#ifndef UI_AURA_WINDOW_TREE_HOST_WIN_H_
+#define UI_AURA_WINDOW_TREE_HOST_WIN_H_
 
 #include "base/compiler_specific.h"
 #include "ui/aura/aura_export.h"
@@ -101,4 +101,4 @@ AURA_EXPORT void SetUsePopupAsRootWindowForTest(bool use);
 
 }  // namespace aura
 
-#endif  // UI_AURA_ROOT_WINDOW_HOST_WIN_H_
+#endif  // UI_AURA_WINDOW_TREE_HOST_WIN_H_