Always create ClientNativePixmapFactory in chrome --mash

ui/gfx/client_native_pixmap_factory.cc

 // Copyright 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/gfx/client_native_pixmap_factory.h"
 
 namespace gfx {
 
 namespace {
 
 ClientNativePixmapFactory* g_instance = nullptr;
 
 }  // namespace
 
 // static
 ClientNativePixmapFactory* ClientNativePixmapFactory::GetInstance() {
   return g_instance;
 }
 
 // static
+void ClientNativePixmapFactory::ResetInstance() {
+  g_instance = nullptr;
+}
+
+// static
 void ClientNativePixmapFactory::SetInstance(
     ClientNativePixmapFactory* instance) {
   DCHECK(!g_instance);
   DCHECK(instance);
   g_instance = instance;
 }
 
 ClientNativePixmapFactory::ClientNativePixmapFactory() {}
 
 ClientNativePixmapFactory::~ClientNativePixmapFactory() {}
 
 }  // namespace gfx