Wipe out QuotaThreadTask.

This is a one of a series of refactoring patches for QuotaManager.
http://codereview.chromium.org/10872054/
http://codereview.chromium.org/10917060/

BUG=139270

Review URL: https://chromiumcodereview.appspot.com/10919070

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@154987 0039d316-1c4b-4281-b951-d872f2087c98
bool QuotaManager::ResetUsageTracker(StorageType type) {
  DCHECK(GetUsageTracker(type));
  if (GetUsageTracker(type)->IsWorking())
    return false;
  switch (type) {
    case kStorageTypeTemporary:
      temporary_usage_tracker_.reset(
          new UsageTracker(clients_, kStorageTypeTemporary,
                           special_storage_policy_));
      return true;
    case kStorageTypePersistent:
      persistent_usage_tracker_.reset(
          new UsageTracker(clients_, kStorageTypePersistent,
                           special_storage_policy_));
      return true;
    default:
      NOTREACHED();
  }
  return true;
}

bool QuotaManager::ResetUsageTracker(StorageType type) {
  DCHECK(GetUsageTracker(type));
  if (GetUsageTracker(type)->IsWorking())
    return false;
  switch (type) {
    case kStorageTypeTemporary:
      temporary_usage_tracker_.reset(
          new UsageTracker(clients_, kStorageTypeTemporary,
                           special_storage_policy_));
      return true;
    case kStorageTypePersistent:
      persistent_usage_tracker_.reset(
          new UsageTracker(clients_, kStorageTypePersistent,
                           special_storage_policy_));
      return true;
    default:
      NOTREACHED();
  }
  return true;
}
