[Sync] Stop dropping pending restarts from interleaved nudges.

components/sync/engine_impl/sync_scheduler_impl.cc

 // Copyright (c) 2012 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 "components/sync/engine_impl/sync_scheduler_impl.h"
 
 #include <algorithm>
 #include <cstring>
 #include <utility>
 
@@ skipping 756 matching lines @@
   // If not a good time, reschedule a new run.
   if (nudge_tracker_.IsSyncRequired() && CanRunNudgeJobNow(NORMAL_PRIORITY))
     TrySyncCycleJob();
   else
     RestartWaiting();
 }
 
 void SyncSchedulerImpl::PerformDelayedNudge() {
   // Circumstances may have changed since we scheduled this delayed nudge.
   // We must check to see if it's OK to run the job before we do so.
-  if (CanRunNudgeJobNow(NORMAL_PRIORITY))
+  if (CanRunNudgeJobNow(NORMAL_PRIORITY)) {
     TrySyncCycleJob();
-
-  // We're not responsible for setting up any retries here.  The functions that
-  // first put us into a state that prevents successful sync cycles (eg. global
-  // throttling, type throttling, network errors, transient errors) will also
-  // setup the appropriate retry logic (eg. retry after timeout, exponential
-  // backoff, retry when the network changes).
+  } else {
+    // If we set |waiting_interal_| while this PerformDelayedNudge was pending
+    // callback scheduled to |retry_timer_|, it's possible we didn't re-schedule
+    // because this PerformDelayedNudge was going to execute sooner. If that's
+    // the case, we need to make sure we setup to waiting callback now.
+    RestartWaiting();
+  }
 }
 
 void SyncSchedulerImpl::ExponentialBackoffRetry() {
   TryCanaryJob();
 }
 
 void SyncSchedulerImpl::NotifyRetryTime(base::Time retry_time) {
   for (auto& observer : *cycle_context_->listeners())
     observer.OnRetryTimeChanged(retry_time);
 }
@@ skipping 170 matching lines @@
 
 #undef SDVLOG_LOC
 
 #undef SDVLOG
 
 #undef SLOG
 
 #undef ENUM_CASE
 
 }  // namespace syncer