sync: Drop fully datatype throttled sync jobs rather than saving them.

This avoids a bug where we loop infinitely with calls to RestartWaiting
with a zero WaitInterval length, which happens in part because we don't 
honour ThrottledDatatypeTracker unthrottle times and rely on seperate
exponential backoff treatment.

BUG=177659


Review URL: https://chromiumcodereview.appspot.com/12386012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@185528 0039d316-1c4b-4281-b951-d872f2087c98
2 files changed