Rename RootWindowHost* to WindowTreeHost*

ui/aura/window_tree_host_delegate.h

Index: ui/aura/window_tree_host_delegate.h
diff --git a/ui/aura/window_tree_host_delegate.h b/ui/aura/window_tree_host_delegate.h
index 308e838a616c49a21958ec177c75550f181811da..4428f51557c8fe8063bef9f5bae7275420b915dd 100644
--- a/ui/aura/window_tree_host_delegate.h
+++ b/ui/aura/window_tree_host_delegate.h
@@ -26,9 +26,9 @@ namespace aura {
 
 class RootWindow;
 
-// A private interface used by RootWindowHost implementations to communicate
+// A private interface used by WindowTreeHost implementations to communicate
 // with their owning RootWindow.
-class AURA_EXPORT RootWindowHostDelegate {
+class AURA_EXPORT WindowTreeHostDelegate {
  public:
   virtual bool OnHostKeyEvent(ui::KeyEvent* event) = 0;
   virtual bool OnHostMouseEvent(ui::MouseEvent* event) = 0;
@@ -55,7 +55,7 @@ class AURA_EXPORT RootWindowHostDelegate {
   virtual ui::EventProcessor* GetEventProcessor() = 0;
 
  protected:
-  virtual ~RootWindowHostDelegate() {}
+  virtual ~WindowTreeHostDelegate() {}
 };
 
 }  // namespace aura