Only include the Hangout Services extension in Google Chrome builds.

NOTRY=true
BUG=291271

Review URL: https://codereview.chromium.org/101323010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241248 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 241248
Revert 241165 "Restore positive responses for "audio/mp4" when a..."

Broke "Google Chrome Win" build.
http://build.chromium.org/p/chromium.chrome/builders/Google%20Chrome%20Win/builds/22060

> Restore positive responses for "audio/mp4" when avc1 is supported.
> 
> This case was broken by r221932/r222995.
> 
> BUG=329065
> TEST=Updated browser_tests.
> R=xhwang@chromium.org
> 
> Review URL: https://codereview.chromium.org/116583002

TBR=ddorwin@chromium.org

Review URL: https://codereview.chromium.org/100213008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241249 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 241249