Make DesktopFactoryOzone instances to respect --ozone-platform

ui/views/widget/desktop_aura/desktop_factory_ozone.cc

 // Copyright 2013 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/views/widget/desktop_aura/desktop_factory_ozone.h"
 
+#include <memory>
+
 #include "base/logging.h"
+#include "ui/ozone/platform_object.h"
 
 namespace views {
 
 // static
-DesktopFactoryOzone* DesktopFactoryOzone::impl_ = NULL;
+DesktopFactoryOzone* DesktopFactoryOzone::impl_ = nullptr;
 
 DesktopFactoryOzone::DesktopFactoryOzone() {
+  DCHECK(!impl_) << "There should only be a single DesktopFactoryOzone.";
+  impl_ = this;
 }
 
 DesktopFactoryOzone::~DesktopFactoryOzone() {
+  DCHECK_EQ(impl_, this);
+  impl_ = nullptr;
 }
 
 DesktopFactoryOzone* DesktopFactoryOzone::GetInstance() {
-  CHECK(impl_) << "DesktopFactoryOzone accessed before constructed";
+  if (!impl_) {
+    std::unique_ptr<DesktopFactoryOzone> factory =
+        ui::PlatformObject<DesktopFactoryOzone>::Create();
+
+    // TODO(tonikitoo): Currently need to leak this object.

[Michael Forney, 2016/06/06 20:08:21]

I wasn't sure about this, but it looks like this is what we currently do for
OzonePlatform, so I guess it's fine.

+    DesktopFactoryOzone* leaky = factory.release();
+    DCHECK_EQ(impl_, leaky);
+  }
   return impl_;
 }
 
-void DesktopFactoryOzone::SetInstance(DesktopFactoryOzone* impl) {
-  impl_ = impl;
-}
-
 } // namespace views