Add a way to specify different source urls for the component updater

So components can be installed from the chrome web store or from
some limited set of options which are controlled by an enum.

Currentlyt the options are omaha (bandaid) the chrome webstore and
the sandbox webstore.

BUG=171079
TEST=see bug, added unittest.
Review URL: https://codereview.chromium.org/11859044

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@178360 0039d316-1c4b-4281-b951-d872f2087c98
5 files changed