Implement cursor compositing mode on Ash

ash/wm/ash_native_cursor_manager.h

Index: ash/wm/ash_native_cursor_manager.h
diff --git a/ash/wm/ash_native_cursor_manager.h b/ash/wm/ash_native_cursor_manager.h
index f307b1663d783d59ce6b4c43476521a9547d781e..6a1e450e830eff55ce538ff1426e8a1b317c2cc9 100644
--- a/ash/wm/ash_native_cursor_manager.h
+++ b/ash/wm/ash_native_cursor_manager.h
@@ -33,6 +33,12 @@ class ASH_EXPORT AshNativeCursorManager
   AshNativeCursorManager();
   virtual ~AshNativeCursorManager();
 
+  // Toggle native cursor enabled/disabled.
+  // The native cursor is enabled by default. When disabled, we hide the native
+  // cursor regardless of visibility state, and let CursorWindowManager draw
+  // the cursor.
+  void SetNativeCursorEnabled(bool enabled);
+
  private:
   friend class test::CursorManagerTestApi;
 
@@ -59,6 +65,8 @@ class ASH_EXPORT AshNativeCursorManager
   // The cursor location where the cursor was disabled.
   gfx::Point disabled_cursor_location_;
 
+  bool native_cursor_enabled_;
+
   scoped_ptr<ImageCursors> image_cursors_;
 
   DISALLOW_COPY_AND_ASSIGN(AshNativeCursorManager);