Adding GitHub repos to doc server

Repos include webstore, devtools, and multidevice.

R=kalman@chromium.org

Review URL: https://codereview.chromium.org/67283005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@234245 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 234245