Move LoaderIOThreadNotifier out of resource_dispatcher_host_impl.h

content/browser/loader/loader_io_thread_notifier.h

+// Copyright 2016 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_BROWSER_LOADER_LOADER_IO_THREAD_NOTIFIER
+#define CONTENT_BROWSER_LOADER_LOADER_IO_THREAD_NOTIFIER
+
+#include "base/macros.h"
+#include "content/public/browser/web_contents_observer.h"
+
+namespace content {
+
+class RenderFrameHost;
+class WebContents;
+
+// This class is responsible for notifying the IO thread (specifically, the
+// ResourceDispatcherHostImpl) of frame events. It has an interace for callers
+// to use and also sends notifications on WebContentsObserver events. All
+// methods (static or class) will be called from the UI thread and post to the
+// IO thread.
+class LoaderIOThreadNotifier : public WebContentsObserver {
+ public:
+  explicit LoaderIOThreadNotifier(WebContents* web_contents);
+  ~LoaderIOThreadNotifier() override;
+
+  // content::WebContentsObserver:
+  void RenderFrameDeleted(RenderFrameHost* render_frame_host) override;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(LoaderIOThreadNotifier);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_LOADER_LOADER_IO_THREAD_NOTIFIER