Move root_window_host* in aura to window_tree_host*.

ui/aura/window_tree_host_mac.h

Index: ui/aura/window_tree_host_mac.h
diff --git a/ui/aura/root_window_host_mac.h b/ui/aura/window_tree_host_mac.h
similarity index 94%
rename from ui/aura/root_window_host_mac.h
rename to ui/aura/window_tree_host_mac.h
index 7cbf0829a8b20a39dd45f808b8a9fa9a5fcae25f..bdd072f3cff47173a7717a64284c4d9db8a69404 100644
--- a/ui/aura/root_window_host_mac.h
+++ b/ui/aura/window_tree_host_mac.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_MAC_H_
-#define UI_AURA_ROOT_WINDOW_HOST_MAC_H_
+#ifndef UI_AURA_WINDOW_TREE_HOST_MAC_H_
+#define UI_AURA_WINDOW_TREE_HOST_MAC_H_
 
 #include <vector>
 
@@ -60,4 +60,4 @@ class AURA_EXPORT WindowTreeHostMac : public WindowTreeHost {
 
 }  // namespace aura
 
-#endif  // UI_AURA_ROOT_WINDOW_HOST_MAC_H_
+#endif  // UI_AURA_WINDOW_TREE_HOST_MAC_H_