ChromiumOS only developers don't always have a Chromium checkout and
a Rietveld cookie file (~/.codereview_upload_cookies) with the auth
keys. This patch proceeds with the activity lookup from other
services such as Gerrit and GoB if there's no Rietveld cookie
present, displaying an error message when this happens.

BUG=chromium:316961
TEST=Remove ~/.codereview_upload_cookies and ran my_activity. ChromeOS activity listed.

Review URL: https://codereview.chromium.org/68763004

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@234874 0039d316-1c4b-4281-b951-d872f2087c98