[Sync] Cleanup all tab sync enabling logic now that its on by default.

BUG=none
TEST=


Review URL: https://chromiumcodereview.appspot.com/10443046

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@139462 0039d316-1c4b-4281-b951-d872f2087c98
    ProfileSyncService::GetSessionModelAssociator() {
  if (data_type_controllers_.find(syncable::SESSIONS) ==
      data_type_controllers_.end() ||
      data_type_controllers_.find(syncable::SESSIONS)->second->state() !=
      DataTypeController::RUNNING) {
    return NULL;
  }
  return static_cast<browser_sync::SessionDataTypeController*>(
      data_type_controllers_.find(
      syncable::SESSIONS)->second.get())->GetModelAssociator();
}

    ProfileSyncService::GetSessionModelAssociator() {
  if (data_type_controllers_.find(syncable::SESSIONS) ==
      data_type_controllers_.end() ||
      data_type_controllers_.find(syncable::SESSIONS)->second->state() !=
      DataTypeController::RUNNING) {
    return NULL;
  }
  return static_cast<browser_sync::SessionDataTypeController*>(
      data_type_controllers_.find(
      syncable::SESSIONS)->second.get())->GetModelAssociator();
}
