Add action for each button on opt-in IME menu.

ui/keyboard/keyboard_controller_observer.h

Index: ui/keyboard/keyboard_controller_observer.h
diff --git a/ui/keyboard/keyboard_controller_observer.h b/ui/keyboard/keyboard_controller_observer.h
index 174d06bb3507f924856d4586ff03c33382419368..7610caefaad6be81a026290e33ea63d35af33e18 100644
--- a/ui/keyboard/keyboard_controller_observer.h
+++ b/ui/keyboard/keyboard_controller_observer.h
@@ -21,6 +21,10 @@ class KEYBOARD_EXPORT KeyboardControllerObserver {
 
   // Called when the keyboard bounds or visibility are about to change.
   virtual void OnKeyboardBoundsChanging(const gfx::Rect& new_bounds) = 0;
+
+  // Called when the keyboard has been hidden and the hiding animation finished
+  // successfully
+  virtual void OnKeyboardHidden() = 0;

[sky, 2016/09/14 18:03:43]

Given most call sites don't care about this is there a reason to make it pure
virtual instead of having an empty implementation?

[Azure Wei, 2016/09/15 03:44:51]

Updated with virtual method with empty implementation. Please take another look.
Thanks. 

 };
 
 }  // namespace keyboard