Fixs bug resulting in double event delivery in mus

ui/aura/mus/input_method_mus.cc

 // Copyright (c) 2015 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 "ui/aura/mus/input_method_mus.h"
 
 #include <utility>
 
 #include "base/memory/ptr_util.h"
 #include "services/ui/public/interfaces/constants.mojom.h"
@@ skipping 69 matching lines @@
 
 bool InputMethodMus::OnUntranslatedIMEMessage(const base::NativeEvent& event,
                                               NativeEventResult* result) {
   // This method is not called on non-Windows platforms. See the comments for
   // ui::InputMethod::OnUntranslatedIMEMessage().
   return false;
 }
 
 void InputMethodMus::DispatchKeyEvent(ui::KeyEvent* event) {
   DispatchKeyEvent(event, nullptr);
+  // Mark the event as handled so that EventGenerator doesn't attempt to
+  // deliver event as well.
+  event->SetHandled();
 }
 
 void InputMethodMus::OnTextInputTypeChanged(const ui::TextInputClient* client) {
   if (IsTextInputClientFocused(client))
     UpdateTextInputType();
   InputMethodBase::OnTextInputTypeChanged(client);
 
   if (input_method_)
     input_method_->OnTextInputTypeChanged(client->GetTextInputType());
 }
@@ skipping 98 matching lines @@
       std::move(pending_callbacks_.front());
   pending_callbacks_.pop_front();
   // |ack_callback| can be null if the standard form of DispatchKeyEvent() is
   // called instead of the version which provides a callback. In mus+ash we
   // use the version with callback, but some unittests use the standard form.
   if (ack_callback)
     ack_callback->Run(event_result);
 }
 
 }  // namespace aura