Remove InputMethodEventHandler.

ash/mus/ash_window_tree_host_mus.h

 // Copyright 2017 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_MUS_ASH_WINDOW_TREE_HOST_MUS_H_
 #define ASH_MUS_ASH_WINDOW_TREE_HOST_MUS_H_
 
 #include "ash/host/ash_window_tree_host.h"
 #include "ui/aura/mus/window_tree_host_mus.h"
 
@@ skipping 18 matching lines @@
   aura::WindowTreeHost* AsWindowTreeHost() override;
   void PrepareForShutdown() override;
   void RegisterMirroringHost(AshWindowTreeHost* mirroring_ash_host) override;
 
   // aura::WindowTreeHostMus:
   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;
-  ui::EventDispatchDetails DispatchKeyEventPostIME(
-      ui::KeyEvent* event) override;
 
  private:
   std::unique_ptr<TransformerHelper> transformer_helper_;
 
   DISALLOW_COPY_AND_ASSIGN(AshWindowTreeHostMus);
 };
 
 }  // namespace ash
 
 #endif  // ASH_MUS_ASH_WINDOW_TREE_HOST_MUS_H_