web-threads: Create a single instance of WebThread for each blink thread.

content/child/webthread_impl.h

Index: content/child/webthread_impl.h
diff --git a/content/child/webthread_impl.h b/content/child/webthread_impl.h
index edd39566e81dc79fc13373c1e1bf2db87d521049..c50295253b473215cd384aa1703920626365cf6f 100644
--- a/content/child/webthread_impl.h
+++ b/content/child/webthread_impl.h
@@ -80,25 +80,6 @@ class CONTENT_EXPORT WebThreadImpl : public WebThreadBase {
   scoped_ptr<base::Thread> thread_;
 };
 
-class WebThreadImplForMessageLoop : public WebThreadBase {
- public:
-  CONTENT_EXPORT explicit WebThreadImplForMessageLoop(
-      scoped_refptr<base::SingleThreadTaskRunner> owning_thread_task_runner);
-  CONTENT_EXPORT virtual ~WebThreadImplForMessageLoop();
-
-  // blink::WebThread implementation.
-  blink::PlatformThreadId threadId() const override;
-
-  // WebThreadBase implementation.
-  base::MessageLoop* MessageLoop() const override;
-
- private:
-  base::SingleThreadTaskRunner* TaskRunner() const override;
-
-  scoped_refptr<base::SingleThreadTaskRunner> owning_thread_task_runner_;
-  blink::PlatformThreadId thread_id_;
-};
-
 } // namespace content
 
 #endif  // CONTENT_CHILD_WEBTHREAD_IMPL_H_