[BackgroundSync Cleanup] Remove power observer

content/browser/background_sync/background_sync.proto

Index: content/browser/background_sync/background_sync.proto
diff --git a/content/browser/background_sync/background_sync.proto b/content/browser/background_sync/background_sync.proto
index 11adc3133c3afafb59ebbc517e47d4aebc8e453f..c6b404552fdb4e2e9f0b65fe374388f72359ebef 100644
--- a/content/browser/background_sync/background_sync.proto
+++ b/content/browser/background_sync/background_sync.proto
@@ -14,11 +14,6 @@ enum SyncNetworkState {
   NETWORK_STATE_ONLINE = 2;
 }
 
-enum SyncPowerState {
-  POWER_STATE_AUTO = 0;
-  POWER_STATE_AVOID_DRAINING = 1;
-}
-
 enum SyncPeriodicity {
   SYNC_PERIODIC = 0;
   SYNC_ONE_SHOT = 1;
@@ -30,7 +25,7 @@ message BackgroundSyncRegistrationProto {
   required SyncPeriodicity periodicity = 3;
   required int64 min_period = 4;
   required SyncNetworkState network_state = 5;
-  required SyncPowerState power_state = 6;
+  // required SyncPowerState power_state = 6;
   required int32 num_attempts = 7;
   required int64 delay_until = 8;
 }