[BackgroundSync Cleanup] Remove power observer

content/public/common/background_sync.mojom

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 module content;
 
 enum BackgroundSyncNetworkState {
   ANY,
   AVOID_CELLULAR,
   ONLINE,
   MAX=ONLINE
 };
 
-enum BackgroundSyncPowerState {
-  AUTO,
-  AVOID_DRAINING,
-  MAX=AVOID_DRAINING
-};
-
 enum BackgroundSyncPeriodicity {
   PERIODIC,
   ONE_SHOT,
   MAX=ONE_SHOT
 };
 
 struct SyncRegistration {
   int64 handle_id = -1;
   BackgroundSyncPeriodicity periodicity = ONE_SHOT;
   string tag = "";
   uint64 min_period_ms = 0;
   BackgroundSyncNetworkState network_state = ONLINE;
-  BackgroundSyncPowerState power_state = AUTO;
 };