Revert of Remove InputMethodEventHandler.

ash/host/ash_window_tree_host.cc

 // Copyright 2014 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.
 
 #include "ash/host/ash_window_tree_host.h"
 
 #include "ash/host/ash_window_tree_host_init_params.h"
 #include "ash/host/ash_window_tree_host_unified.h"
 #include "ash/shell_port.h"
 #include "base/memory/ptr_util.h"
 #include "ui/aura/client/screen_position_client.h"
 #include "ui/aura/window_tree_host.h"
 #include "ui/events/event.h"
 #include "ui/gfx/geometry/rect.h"
 
 #if defined(USE_OZONE)
 #include "ash/host/ash_window_tree_host_platform.h"
 #elif defined(USE_X11)
 #include "ash/host/ash_window_tree_host_x11.h"
 #endif
 
 namespace ash {
 
-AshWindowTreeHost::AshWindowTreeHost() {}
+AshWindowTreeHost::AshWindowTreeHost() : input_method_handler_(nullptr) {}
 
 AshWindowTreeHost::~AshWindowTreeHost() = default;
 
 void AshWindowTreeHost::TranslateLocatedEvent(ui::LocatedEvent* event) {
   if (event->IsTouchEvent())
     return;
 
   aura::WindowTreeHost* wth = AsWindowTreeHost();
   aura::Window* root_window = wth->window();
   aura::client::ScreenPositionClient* screen_position_client =
@@ skipping 31 matching lines @@
   return base::MakeUnique<AshWindowTreeHostPlatform>(
       init_params.initial_bounds);
 #elif defined(USE_X11)
   return base::MakeUnique<AshWindowTreeHostX11>(init_params.initial_bounds);
 #else
 #error Unsupported platform.
 #endif
 }
 
 }  // namespace ash