[Sync] Fix bug leading to ProfileSyncService test flakiness
The bug was that an IO thread wasn't present for
NonBlockingInvalidationNotifier::Core::Initialize() to be posted,
but was present for other functions, leading to a crash.
Add IO thread to various unit tests.
Add NOTREACHED() calls for NonBlockingInvalidationNotifier posts.
BUG=79757
TEST=
Review URL: http://codereview.chromium.org/6893013
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@82994 0039d316-1c4b-4281-b951-d872f2087c98
12 files changed
