[Sync] Add tests for invalid specifics field number handling
This is a follow up to r172232.
Change NOTREACHED() to DLOG(WARNING), since the server sending down
unknown/invalid field numbers is a valid event.
Add tests for the code that uses GetModelTypeFromSpecificsFieldNumber().
Clean up some code in sync/engine/ a bit.
BUG=165171
Review URL: https://chromiumcodereview.appspot.com/11485019
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@172816 0039d316-1c4b-4281-b951-d872f2087c98
9 files changed