Switch DRM platform to using a separate thread

ui/ozone/platform/drm/gpu/proxy_helpers.h

+// 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.
+
+#ifndef UI_OZONE_PLATFORM_DRM_GPU_PROXY_HELPERS_H_
+#define UI_OZONE_PLATFORM_DRM_GPU_PROXY_HELPERS_H_
+
+#include "base/bind.h"
+#include "base/location.h"
+#include "base/memory/ref_counted.h"
+#include "base/thread_task_runner_handle.h"
+
+namespace ui {
+
+namespace internal {
+
+template <typename... Args>
+void PostAsyncTask(
+    const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
+    const base::Callback<void(Args...)>& callback,
+    Args... args) {
+  task_runner->PostTask(FROM_HERE, base::Bind(callback, args...));
+}
+
+}  // namespace internal
+
+// Posts a task to a different thread and blocks waiting for the task to finish
+// executing.
+void PostSyncTask(
+    const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
+    const base::Closure& callback);
+
+// Creates a callback that will run |callback| on the calling thread. Useful
+// when posting a task on a different thread and expecting a callback when the
+// task finished (and the callback needs to run on the original thread).
+template <typename... Args>
+base::Callback<void(Args...)> CreateSafeCallback(
+    const base::Callback<void(Args...)>& callback) {
+  return base::Bind(&internal::PostAsyncTask<Args...>,
+                    base::ThreadTaskRunnerHandle::Get(), callback);
+}
+
+}  // namespace ui
+
+#endif  // UI_OZONE_PLATFORM_DRM_GPU_PROXY_HELPERS_H_