Revert of Remove InputMethodEventHandler.

ash/host/ash_window_tree_host_platform.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ASH_HOST_ASH_WINDOW_TREE_HOST_PLATFORM_H_
 #define ASH_HOST_ASH_WINDOW_TREE_HOST_PLATFORM_H_
 
 #include <memory>
 
 #include "ash/ash_export.h"
@@ skipping 24 matching lines @@
   void PrepareForShutdown() override;
   void SetRootTransform(const gfx::Transform& transform) override;
   gfx::Transform GetRootTransform() const override;
   gfx::Transform GetInverseRootTransform() const override;
   void UpdateRootWindowSizeInPixels(
       const gfx::Size& host_size_in_pixels) override;
   void OnCursorVisibilityChangedNative(bool show) override;
   void SetBoundsInPixels(const gfx::Rect& bounds) override;
   void DispatchEvent(ui::Event* event) override;
 
+  // ui::internal::InputMethodDelegate:
+  ui::EventDispatchDetails DispatchKeyEventPostIME(
+      ui::KeyEvent* event) override;
+
  private:
   // Temporarily disable the tap-to-click feature. Used on CrOS.
   void SetTapToClickPaused(bool state);
 
   TransformerHelper transformer_helper_;
 
   DISALLOW_COPY_AND_ASSIGN(AshWindowTreeHostPlatform);
 };
 
 }  // namespace ash
 
 #endif  // ASH_HOST_ASH_WINDOW_TREE_HOST_PLATFORM_H_