Don't pass touches to gesture recognizer for async acks.

ui/aura/window_tree_host.h

Index: ui/aura/window_tree_host.h
diff --git a/ui/aura/window_tree_host.h b/ui/aura/window_tree_host.h
index aaf0d3b265c9973518ba7b3e9791f46d214a6290..4f26fa3547a42336792defbdb2469cb9d3531300 100644
--- a/ui/aura/window_tree_host.h
+++ b/ui/aura/window_tree_host.h
@@ -169,6 +169,8 @@ class AURA_EXPORT WindowTreeHost {
   // kCalled when the cursor visibility has changed.
   virtual void OnCursorVisibilityChangedNative(bool show) = 0;
 
+  scoped_ptr<WindowEventDispatcher> dispatcher_;
+
  private:
   friend class test::WindowTreeHostTestApi;
 
@@ -185,8 +187,6 @@ class AURA_EXPORT WindowTreeHost {
 
   ObserverList<WindowTreeHostObserver> observers_;
 
-  scoped_ptr<WindowEventDispatcher> dispatcher_;
-
   scoped_ptr<ui::Compositor> compositor_;
 
   // Last cursor set.  Used for testing.