sync: Refactor per-datatype throttling

sync/engine/syncer_proto_util.h

Index: sync/engine/syncer_proto_util.h
diff --git a/sync/engine/syncer_proto_util.h b/sync/engine/syncer_proto_util.h
index 14a3791325edc8dc72794db87db28cc2e53b091e..3856509922701e5e6de5a7bd8258cdd7791e5e50 100644
--- a/sync/engine/syncer_proto_util.h
+++ b/sync/engine/syncer_proto_util.h
@@ -33,6 +33,7 @@ class SyncSessionContext;
 }
 
 class ClientToServerMessage;
+class ThrottledDataTypeTracker;
 class ServerConnectionManager;
 class SyncEntity;
 class CommitResponse_EntryResponse;
@@ -118,10 +119,11 @@ class SyncerProtoUtil {
   static base::TimeDelta GetThrottleDelay(
       const sync_pb::ClientToServerResponse& response);
 
-  static void HandleThrottleError(const SyncProtocolError& error,
-                                  const base::TimeTicks& throttled_until,
-                                  sessions::SyncSessionContext* context,
-                                  sessions::SyncSession::Delegate* delegate);
+  static void HandleThrottleError(
+      const SyncProtocolError& error,
+      const base::TimeTicks& throttled_until,
+      browser_sync::ThrottledDataTypeTracker* tracker,
+      sessions::SyncSession::Delegate* delegate);
 
   friend class SyncerProtoUtilTest;
   FRIEND_TEST_ALL_PREFIXES(SyncerProtoUtilTest, AddRequestBirthday);