Add srcObject attribute of type MediaStream to HTMLMediaElement.

content/renderer/media/web_media_element_source_utils.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_RENDERER_MEDIA_WEB_MEDIA_ELEMENT_SOURCE_UTILS_H_
+#define CONTENT_RENDERER_MEDIA_WEB_MEDIA_ELEMENT_SOURCE_UTILS_H_
+
+namespace blink {
+class WebMediaPlayerSource;
+class WebMediaStream;
+}
+
+namespace content {
+
+// Obtains a WebMediaStream from a WebMediaPlayerSource. If the
+// WebMediaPlayerSource does not contain a WebMediaStream, a null
+// WebMediaStream is returned.
+blink::WebMediaStream GetWebMediaStreamFromWebMediaPlayerSource(
+    const blink::WebMediaPlayerSource& source);
+
+}  // namespace content
+
+#endif  // CONTENT_RENDERER_MEDIA_WEB_MEDIA_ELEMENT_SOURCE_UTILS_H_