Refactor: Make MediaCaptureDevicesDispatcher have pluggable handlers.

chrome/browser/media/media_access_handler.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 CHROME_BROWSER_MEDIA_MEDIA_ACCESS_HANDLER_H_
+#define CHROME_BROWSER_MEDIA_MEDIA_ACCESS_HANDLER_H_
+
+#include "base/callback.h"
+#include "content/public/browser/media_request_state.h"
+#include "content/public/common/media_stream_request.h"
+
+namespace content {
+class WebContents;
+}
+
+namespace extensions {
+class Extension;
+}
+
+// Interface for handling media access requests that are propagated from
+// MediaCaptureDevicesDispatcher.
+class MediaAccessHandler {
+ public:
+  MediaAccessHandler() {}
+  virtual ~MediaAccessHandler() {}
+
+  // Check if the media stream type is supported by MediaAccessHandler.
+  virtual bool SupportsStreamType(const content::MediaStreamType type,
+                                  const extensions::Extension* extension) = 0;
+  // Check media access permission. |extension| is set to NULL if request was
+  // made from a drive-by page.
+  virtual bool CheckMediaAccessPermission(
+      content::WebContents* web_contents,
+      const GURL& security_origin,
+      content::MediaStreamType type,
+      const extensions::Extension* extension) = 0;
+  // Process media access requests. |extension| is set to NULL if request was
+  // made from a drive-by page.
+  virtual void HandleRequest(content::WebContents* web_contents,
+                             const content::MediaStreamRequest& request,
+                             const content::MediaResponseCallback& callback,
+                             const extensions::Extension* extension) = 0;
+  // Update media request state. Called on UI thread.
+  virtual void UpdateMediaRequestState(int render_process_id,
+                                       int render_frame_id,
+                                       int page_request_id,
+                                       content::MediaStreamType stream_type,
+                                       content::MediaRequestState state) {}
+};
+
+#endif  // CHROME_BROWSER_MEDIA_MEDIA_ACCESS_HANDLER_H_