MediaStream API: Getting rid of exceptions in code/DEPS
To be able to do so I had to store a pointer to the MediaStreamRegistry
in HTMLMediaElement. Not a very elegant solution but I could not figure
out any other way to fix this.

Review URL: https://codereview.chromium.org/138883005

git-svn-id: svn://svn.chromium.org/blink/trunk@166317 bbb929c8-8fbe-4397-9dbb-9b2b20218538