sync: Add pre-commit update avoidance mode + flag

sync/sessions/data_type_tracker.cc

 // Copyright 2013 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.
 
 #include "sync/sessions/data_type_tracker.h"
 
 #include "base/logging.h"
 #include "sync/sessions/nudge_tracker.h"
 
 namespace syncer {
@@ skipping 41 matching lines @@
 
 // This limit will take effect on all future invalidations received.
 void DataTypeTracker::UpdatePayloadBufferSize(size_t new_size) {
   payload_buffer_size_ = new_size;
 }
 
 bool DataTypeTracker::IsSyncRequired() const {
   return !IsThrottled() &&
       (local_nudge_count_ > 0 ||
        local_refresh_request_count_ > 0 ||
-       !pending_payloads_.empty());
+       HasPendingInvalidation() ||
+       local_payload_overflow_ ||
+       server_payload_overflow_);
+}
+
+bool DataTypeTracker::IsGetUpdatesRequired() const {
+  return !IsThrottled() &&
+      (local_refresh_request_count_ > 0 ||
+       HasPendingInvalidation() ||
+       local_payload_overflow_ ||
+       server_payload_overflow_);
 }
 
 bool DataTypeTracker::HasLocalChangePending() const {
   return local_nudge_count_ > 0;
 }
 
 bool DataTypeTracker::HasPendingInvalidation() const {
   return !pending_payloads_.empty();
 }
 
@@ skipping 56 matching lines @@
 }
 
 void DataTypeTracker::UpdateThrottleState(base::TimeTicks now) {
   if (now >= unthrottle_time_) {
     unthrottle_time_ = base::TimeTicks();
   }
 }
 
 }  // namespace sessions
 }  // namespace syncer