Use EventHandler for IME

ash/host/ash_window_tree_host.h

Index: ash/host/ash_window_tree_host.h
diff --git a/ash/host/ash_window_tree_host.h b/ash/host/ash_window_tree_host.h
index fab7afd1f7bbde725f594175eb5ed6a8f45f9cd7..54724aa5fcf9224d43fdba04e571375d7ff004b0 100644
--- a/ash/host/ash_window_tree_host.h
+++ b/ash/host/ash_window_tree_host.h
@@ -19,21 +19,33 @@ class Rect;
 }
 
 namespace ui {
+class EventSource;
+class KeyEvent;
 class LocatedEvent;
 }
 
 namespace ash {
 struct AshWindowTreeHostInitParams;
+class InputMethodEventHandler;
 class RootWindowTransformer;
 
 class ASH_EXPORT AshWindowTreeHost {
  public:
+  AshWindowTreeHost();
   virtual ~AshWindowTreeHost() {}
 
   // Creates a new AshWindowTreeHost. The caller owns the returned value.
   static AshWindowTreeHost* Create(
       const AshWindowTreeHostInitParams& init_params);
 
+  void set_input_method_handler(InputMethodEventHandler* input_method_handler) {
+    input_method_handler_ = input_method_handler;
+  }
+
+  InputMethodEventHandler* input_method_handler() {
+    return input_method_handler_;
+  }
+
   // Toggles the host's full screen state.
   virtual void ToggleFullScreen() = 0;
 
@@ -60,6 +72,9 @@ class ASH_EXPORT AshWindowTreeHost {
  protected:
   // Translates the native mouse location into screen coordinates.
   void TranslateLocatedEvent(ui::LocatedEvent* event);
+
+ private:
+  InputMethodEventHandler* input_method_handler_;
 };
 
 }  // namespace ash