sync: Gracefully handle very early shutdown

sync/engine/syncer.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 "sync/engine/syncer.h"
 
 #include "base/debug/trace_event.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
 #include "base/time/time.h"
 #include "build/build_config.h"
 #include "sync/engine/apply_control_data_updates.h"
 #include "sync/engine/apply_updates_and_resolve_conflicts_command.h"
 #include "sync/engine/build_commit_command.h"
 #include "sync/engine/commit.h"
 #include "sync/engine/conflict_resolver.h"
 #include "sync/engine/download.h"
 #include "sync/engine/net/server_connection_manager.h"
 #include "sync/engine/process_commit_response_command.h"
 #include "sync/engine/syncer_types.h"
+#include "sync/internal_api/public/base/cancellation_signal.h"
 #include "sync/internal_api/public/base/unique_position.h"
 #include "sync/internal_api/public/util/syncer_error.h"
 #include "sync/sessions/nudge_tracker.h"
 #include "sync/syncable/mutable_entry.h"
 #include "sync/syncable/syncable-inl.h"
 
 using base::Time;
 using base::TimeDelta;
 using sync_pb::ClientCommand;
 
 namespace syncer {
 
 // TODO(akalin): We may want to propagate this switch up
 // eventually.
 #if defined(OS_ANDROID) || defined(OS_IOS)
 static const bool kCreateMobileBookmarksFolder = true;
 #else
 static const bool kCreateMobileBookmarksFolder = false;
 #endif
 
 using sessions::StatusController;
 using sessions::SyncSession;
 using sessions::NudgeTracker;
 
-Syncer::Syncer()
-    : early_exit_requested_(false) {
+Syncer::Syncer(syncer::CancellationSignal* cancellation_signal)
+    : cancellation_signal_(cancellation_signal) {
 }
 
 Syncer::~Syncer() {}
 
 bool Syncer::ExitRequested() {
-  base::AutoLock lock(early_exit_requested_lock_);
-  return early_exit_requested_;
-}
-
-void Syncer::RequestEarlyExit() {
-  base::AutoLock lock(early_exit_requested_lock_);
-  early_exit_requested_ = true;
+  return cancellation_signal_->IsStopRequested();
 }
 
 bool Syncer::NormalSyncShare(ModelTypeSet request_types,
                              const NudgeTracker& nudge_tracker,
                              SyncSession* session) {
   HandleCycleBegin(session);
   VLOG(1) << "Downloading types " << ModelTypeSetToString(request_types);
   if (nudge_tracker.IsGetUpdatesRequired() ||
       session->context()->ShouldFetchUpdatesBeforeCommit()) {
     if (!DownloadAndApplyUpdates(
@@ skipping 89 matching lines @@
     sync_pb::GetUpdatesCallerInfo::GetUpdatesSource source) {
   if (!ExitRequested()) {
     session->SendSyncCycleEndEventNotification(source);
     return true;
   } else {
     return false;
   }
 }
 
 }  // namespace syncer