Switch DRM platform to using a separate thread

ui/ozone/platform/drm/gpu/drm_vsync_provider.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 "ui/ozone/platform/drm/gpu/drm_vsync_provider.h"
 
 #include "ui/ozone/platform/drm/gpu/drm_window.h"
+#include "ui/ozone/platform/drm/gpu/proxy_helpers.h"
 
 namespace ui {
 
-DrmVSyncProvider::DrmVSyncProvider(DrmWindow* window) : window_(window) {
-}
+DrmVSyncProvider::DrmVSyncProvider(
+    const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
+    base::WeakPtr<DrmWindow> window)
+    : task_runner_(task_runner), window_(window) {}
 
 DrmVSyncProvider::~DrmVSyncProvider() {
 }
 
 void DrmVSyncProvider::GetVSyncParameters(const UpdateVSyncCallback& callback) {
-  window_->GetVSyncParameters(callback);
+  task_runner_->PostTask(FROM_HERE,
+                         base::Bind(&DrmWindow::GetVSyncParameters, window_,
+                                    CreateSafeCallback(callback)));
 }
 
 }  // namespace ui