Fix the MessageLoop type in case more than one ozone platform is built

ui/ozone/public/ozone_platform.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 "base/command_line.h"
 #include "base/logging.h"
 #include "base/trace_event/trace_event.h"
 #include "ui/events/devices/device_data_manager.h"
 #include "ui/ozone/platform_object.h"
 #include "ui/ozone/platform_selection.h"
@@ skipping 76 matching lines @@
   }
 }
 
 // static
 OzonePlatform* OzonePlatform::instance_;
 
 // Convenience methods to facilitate transitionning to new API.
 void OzonePlatform::InitializeUI(const InitParams& args) {
   InitializeUI();
 }
+
 void OzonePlatform::InitializeGPU(const InitParams& args) {
   InitializeGPU();
 }
 
 IPC::MessageFilter* OzonePlatform::GetGpuMessageFilter() {
   return nullptr;
 }
+
+base::MessageLoop::Type OzonePlatform::GetMessageLoopTypeForGpu() {
+  return base::MessageLoop::TYPE_DEFAULT;
+}
+
 void OzonePlatform::AddInterfaces(
     service_manager::InterfaceRegistry* registry) {}
 
 }  // namespace ui