Now ignores obsolete sync nodes without visit transitions.

Also removed assertion that was erroneously triggered by obsolete sync nodes.

BUG=none
TEST=run chrome against a database that contains obsolete typed url sync nodes.

Review URL: http://codereview.chromium.org/7129069

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@88846 0039d316-1c4b-4281-b951-d872f2087c98
void TypedUrlModelAssociator::Disassociate(int64 sync_id) {
  DCHECK(expected_loop_ == MessageLoop::current());
  SyncIdToTypedUrlMap::iterator iter = id_map_inverse_.find(sync_id);
  if (iter == id_map_inverse_.end())
    return;
  CHECK(id_map_.erase(iter->second));
  id_map_inverse_.erase(iter);
}

void TypedUrlModelAssociator::Disassociate(int64 sync_id) {
  DCHECK(expected_loop_ == MessageLoop::current());
  SyncIdToTypedUrlMap::iterator iter = id_map_inverse_.find(sync_id);
  if (iter == id_map_inverse_.end())
    return;
  CHECK(id_map_.erase(iter->second));
  id_map_inverse_.erase(iter);
}
