Adding WebThread and new BlinkPlatformImpl for utility thread.

content/utility/utility_blink_platform_impl.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 CONTENT_UTILITY_UTILITY_BLINK_PLATFORM_IMPL_H_
+#define CONTENT_UTILITY_UTILITY_BLINK_PLATFORM_IMPL_H_
+
+#include "content/child/blink_platform_impl.h"
+
+namespace content {
+
+class WebThreadImplForUtilityThread;
+
+class UtilityBlinkPlatformImpl : public BlinkPlatformImpl {
+ public:
+  UtilityBlinkPlatformImpl();
+  ~UtilityBlinkPlatformImpl() override;
+
+  // BlinkPlatformImpl implementation.
+  blink::WebThread* currentThread() override;
+
+ private:
+  scoped_ptr<WebThreadImplForUtilityThread> main_thread_;
+
+  DISALLOW_COPY_AND_ASSIGN(UtilityBlinkPlatformImpl);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_UTILITY_UTILITY_BLINK_PLATFORM_IMPL_H_