Revert of Remove InputMethodEventHandler.

ash/display/window_tree_host_manager.h

Index: ash/display/window_tree_host_manager.h
diff --git a/ash/display/window_tree_host_manager.h b/ash/display/window_tree_host_manager.h
index 545ae6e2be860f3b3d72d4211640d7953395e03e..df1e96b1095cf85db8a81cee2f909e297763ca3b 100644
--- a/ash/display/window_tree_host_manager.h
+++ b/ash/display/window_tree_host_manager.h
@@ -39,6 +39,7 @@
 struct AshWindowTreeHostInitParams;
 class CursorWindowController;
 class FocusActivationStore;
+class InputMethodEventHandler;
 class MirrorWindowController;
 class RootWindowController;
 
@@ -159,6 +160,10 @@
   ui::EventDispatchDetails DispatchKeyEventPostIME(
       ui::KeyEvent* event) override;
 
+  InputMethodEventHandler* input_method_event_handler() {
+    return input_method_event_handler_.get();
+  }
+
  private:
   FRIEND_TEST_ALL_PREFIXES(WindowTreeHostManagerTest, BoundsUpdated);
   FRIEND_TEST_ALL_PREFIXES(WindowTreeHostManagerTest, SecondaryDisplayLayout);
@@ -190,6 +195,7 @@
   std::unique_ptr<MirrorWindowController> mirror_window_controller_;
 
   std::unique_ptr<ui::InputMethod> input_method_;
+  std::unique_ptr<InputMethodEventHandler> input_method_event_handler_;
 
   // Stores the current cursor location (in native coordinates and screen
   // coordinates respectively). The locations are used to restore the cursor