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

ash/common/shelf/shelf_layout_manager.cc

Index: ash/common/shelf/shelf_layout_manager.cc
diff --git a/ash/common/shelf/shelf_layout_manager.cc b/ash/common/shelf/shelf_layout_manager.cc
index 92a4c75ae32c3f900e096a6746fff05c385af228..8a87a7ec3861411216f6a6d8a4ec66c259ef8e43 100644
--- a/ash/common/shelf/shelf_layout_manager.cc
+++ b/ash/common/shelf/shelf_layout_manager.cc
@@ -419,6 +419,8 @@ void ShelfLayoutManager::OnKeyboardBoundsChanging(const gfx::Rect& new_bounds) {
   }
 }
 
+void ShelfLayoutManager::OnKeyboardHidden() {}
+
 bool ShelfLayoutManager::IsHorizontalAlignment() const {
   return ::ash::IsHorizontalAlignment(GetAlignment());
 }