GitLab

Revert to the old behavior of WaitUntil such that it returns True when the
callable succeeds (default). Provide a way for it to return the last return
value of the callable if required.

TBR=stanleyw@chromium.org
BUG=

Review URL: https://chromiumcodereview.appspot.com/10854229

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@152368 0039d316-1c4b-4281-b951-d872f2087c98