Add srcObject attribute of type MediaStream to HTMLMediaElement.

third_party/WebKit/Source/modules/mediastream/HTMLMediaElementMediaStream.idl

Index: third_party/WebKit/Source/modules/mediastream/HTMLMediaElementMediaStream.idl
diff --git a/third_party/WebKit/Source/modules/mediastream/HTMLMediaElementMediaStream.idl b/third_party/WebKit/Source/modules/mediastream/HTMLMediaElementMediaStream.idl
new file mode 100644
index 0000000000000000000000000000000000000000..3beddfdc51f70d1e7508a8b078e5f88e7e890f7f
--- /dev/null
+++ b/third_party/WebKit/Source/modules/mediastream/HTMLMediaElementMediaStream.idl
@@ -0,0 +1,11 @@
+// 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.
+
+// https://html.spec.whatwg.org/multipage/embedded-content.html#dom-media-srcobject
+
+[
+    RuntimeEnabled=SrcObject
+] partial interface HTMLMediaElement {

[haraken, 2016/03/18 23:37:40]

Would you add:

  // TODO(haraken): Per the spec, the srcObject should be defined in
HTMLMediaElement.idl. However, we cannot define srcObject in
HTMLMediaElement.idl because of the dependency restriction from modules/ to
core/. For now we avoid the problem by using a partial interface.

[Guido Urdaneta, 2016/03/20 12:16:30]

Done.

+    attribute MediaStream? srcObject;

[haraken, 2016/03/18 23:37:40]

The spec says that the type is MediaProvider?. Is it okay to use MediaStream? ?

[Guido Urdaneta, 2016/03/20 12:16:30]

Now using MediaProvider, which is typedef'ed to be MediaStream for now.
According to the spec, it can be MediaStream, MediaSource or Blob.
For now we support only MediaStream, but added a TODO to support the other types
mentioned in the spec. 
As I explain in the I2I, supporting MediaStream puts us at the same level of
support of all the other major browsers.

+};