Add srcObject attribute of type MediaStream to HTMLMediaElement.

third_party/WebKit/public/platform/WebMediaElementSource.h

Index: third_party/WebKit/public/platform/WebMediaElementSource.h
diff --git a/third_party/WebKit/public/platform/WebMediaElementSource.h b/third_party/WebKit/public/platform/WebMediaElementSource.h
new file mode 100644
index 0000000000000000000000000000000000000000..96fd9f29704954d94affa39d026f37186fddcfce
--- /dev/null
+++ b/third_party/WebKit/public/platform/WebMediaElementSource.h
@@ -0,0 +1,38 @@
+// 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 WebMediaElementSource_h
+#define WebMediaElementSource_h
+
+#include "WebCommon.h"
+#include "WebMediaStream.h"
+#include "WebURL.h"
+
+namespace blink {
+
+class BLINK_PLATFORM_EXPORT WebMediaElementSource {
+public:
+    WebMediaElementSource();
+    explicit WebMediaElementSource(const WebURL&);
+    explicit WebMediaElementSource(const WebMediaStream&);
+    ~WebMediaElementSource();
+
+    bool isEmpty() const;
+
+    bool isURL() const;
+    WebURL getAsURL() const;
+
+    bool isMediaProviderObject() const;
+
+    bool isMediaStream() const;
+    WebMediaStream getAsMediaStream() const;
+
+private:
+    WebURL m_url;
+    WebMediaStream m_mediaStream;

[philipj_slow, 2016/03/29 13:43:19]

Is it possible to get the original MediaStream back from a WebMediaStream? If it
is, then it should be possible to let WebMediaElementSource be the only thing
that keeps it alive, which would be more like how I hope this will finally look
like, and will also mean that HTMLMediaElementSrcObject doesn't need to be a
supplement since the HTMLMediaElement itself will hold on to the
WebMediaElementSource object.

[Guido Urdaneta, 2016/03/29 14:48:11]

I just noticed it is possible to get the MediaStream from WebMediaStream as a
MediaStreamDescriptorClient. Updated HTMLMediaElementSrcObject to no longer be a
supplement.

+};
+
+} // namespace blink
+
+#endif // WebMediaElementSource_h