Rename RootWindowHost to WindowTreeHost

ui/aura/root_window_host_mac.h

Index: ui/aura/root_window_host_mac.h
diff --git a/ui/aura/root_window_host_mac.h b/ui/aura/root_window_host_mac.h
index 20454f01897af155de039228cf0005f92384d55b..7cbf0829a8b20a39dd45f808b8a9fa9a5fcae25f 100644
--- a/ui/aura/root_window_host_mac.h
+++ b/ui/aura/root_window_host_mac.h
@@ -23,13 +23,13 @@ namespace internal {
 class TouchEventCalibrate;
 }
 
-class AURA_EXPORT RootWindowHostMac : public RootWindowHost {
+class AURA_EXPORT WindowTreeHostMac : public WindowTreeHost {
  public:
-  explicit RootWindowHostMac(const gfx::Rect& bounds);
-  virtual ~RootWindowHostMac();
+  explicit WindowTreeHostMac(const gfx::Rect& bounds);
+  virtual ~WindowTreeHostMac();
 
  private:
-  // RootWindowHost Overrides.
+  // WindowTreeHost Overrides.
   virtual RootWindow* GetRootWindow() OVERRIDE;
   virtual gfx::AcceleratedWidget GetAcceleratedWidget() OVERRIDE;
   virtual void Show() OVERRIDE;
@@ -55,7 +55,7 @@ class AURA_EXPORT RootWindowHostMac : public RootWindowHost {
  private:
   base::scoped_nsobject<NSWindow> window_;
 
-  DISALLOW_COPY_AND_ASSIGN(RootWindowHostMac);
+  DISALLOW_COPY_AND_ASSIGN(WindowTreeHostMac);
 };
 
 }  // namespace aura