Adding WebThread and new BlinkPlatformImpl for utility thread.

content/utility/webthread_impl_for_utility_thread.h

Index: content/utility/webthread_impl_for_utility_thread.h
diff --git a/content/utility/webthread_impl_for_utility_thread.h b/content/utility/webthread_impl_for_utility_thread.h
new file mode 100644
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+++ b/content/utility/webthread_impl_for_utility_thread.h
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+// 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_WEBTHREAD_IMPL_FOR_UTILITY_THREAD_H_
+#define CONTENT_UTILITY_WEBTHREAD_IMPL_FOR_UTILITY_THREAD_H_
+
+#include "base/memory/ref_counted.h"
+#include "components/scheduler/child/webthread_base.h"
+
+namespace content {
+
+class WebThreadImplForUtilityThread : public scheduler::WebThreadBase {
+ public:
+  WebThreadImplForUtilityThread();
+  ~WebThreadImplForUtilityThread() override;
+
+  // blink::WebThread implementation.
+  blink::WebScheduler* scheduler() const override;
+  blink::PlatformThreadId threadId() const override;
+
+  // WebThreadBase implementation.
+  base::SingleThreadTaskRunner* TaskRunner() const override;
+  scheduler::SingleThreadIdleTaskRunner* IdleTaskRunner() const override;
+
+ private:
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+  blink::PlatformThreadId thread_id_;
+
+  DISALLOW_COPY_AND_ASSIGN(WebThreadImplForUtilityThread);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_UTILITY_WEBTHREAD_IMPL_FOR_UTILITY_THREAD_H_