Implement virtual keyboard hiding.

ash/root_window_controller.h

Index: ash/root_window_controller.h
diff --git a/ash/root_window_controller.h b/ash/root_window_controller.h
index a3d99a368c778402786d9e042fba63b1570d6cbf..49ce6b89f89ab2d10e90b6fb5f1c2c68a7e9bda2 100644
--- a/ash/root_window_controller.h
+++ b/ash/root_window_controller.h
@@ -102,6 +102,10 @@ class ASH_EXPORT RootWindowController : public ShellObserver {
     return always_on_top_controller_.get();
   }
 
+  keyboard::KeyboardController* keyboard_controller() {
+    return keyboard_controller_.get();
+  }
+
   ScreenDimmer* screen_dimmer() { return screen_dimmer_.get(); }
 
   // Access the shelf associated with this root window controller,