[BackgroundSync Cleanup] Remove periodic sync code

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 c6b404552fdb4e2e9f0b65fe374388f72359ebef..62dbe72b359a73ce216f850ab428819152085e80 100644
--- a/content/browser/background_sync/background_sync.proto
+++ b/content/browser/background_sync/background_sync.proto
@@ -14,16 +14,11 @@ enum SyncNetworkState {
   NETWORK_STATE_ONLINE = 2;
 }
 
-enum SyncPeriodicity {
-  SYNC_PERIODIC = 0;
-  SYNC_ONE_SHOT = 1;
-}
-
 message BackgroundSyncRegistrationProto {
   required int64 id = 1;
   required string tag = 2;
-  required SyncPeriodicity periodicity = 3;
-  required int64 min_period = 4;
+  // required SyncPeriodicity periodicity = 3;
+  // required int64 min_period = 4;
   required SyncNetworkState network_state = 5;
   // required SyncPowerState power_state = 6;
   required int32 num_attempts = 7;