Worker changes to prepare for lock-free shutdown.

sync/internal_api/public/engine/model_safe_worker.cc

Index: sync/internal_api/public/engine/model_safe_worker.cc
diff --git a/sync/internal_api/public/engine/model_safe_worker.cc b/sync/internal_api/public/engine/model_safe_worker.cc
index d7bf906ef9f007feec43925789b22a3367a3e15c..49655ff0e3cb7ce8d3285223d7281b1a984abf2e 100644
--- a/sync/internal_api/public/engine/model_safe_worker.cc
+++ b/sync/internal_api/public/engine/model_safe_worker.cc
@@ -80,6 +80,57 @@ std::string ModelSafeGroupToString(ModelSafeGroup group) {
   }
 }
 
+ModelSafeWorker::ModelSafeWorker(WorkerLoopDestructionObserver* observer)
+    : stopped_(false),
+      work_done_or_stopped_(false, false),
+      observer_(observer) {}
+
 ModelSafeWorker::~ModelSafeWorker() {}
 
+void ModelSafeWorker::RequestStop() {
+  base::AutoLock al(lock_);
+
+  // Set stop flag but don't signal work_done_or_stopped_ to unblock sync loop
+  // because the worker may be working and depending on sync command object
+  // living on sync thread.
+  stopped_ = true;
+}
+
+SyncerError ModelSafeWorker::DoWorkAndWaitUntilDone(const WorkCallback& work) {
+  {
+    base::AutoLock al(lock_);
+    if (stopped_)
+      return CANNOT_DO_WORK;
+
+    // Clear signal before starting work.
+    work_done_or_stopped_.Reset();
+  }
+
+  return DoWorkAndWaitUntilDoneImpl(work, &work_done_or_stopped_);
+}
+
+bool ModelSafeWorker::IsStopped() {
+  base::AutoLock al(lock_);
+  return stopped_;
+}
+
+void ModelSafeWorker::WillDestroyCurrentMessageLoop() {
+  {
+    base::AutoLock al(lock_);
+    stopped_ = true;
+
+    // Safe to signal because pending work (if any) will not be executed. So
+    // there should be no harm even the work holds a pointer to the
+    // ModelChangingSyncerCommand that will be destroyed on sync loop after
+    // the signal is set.
+    work_done_or_stopped_.Signal();
+
+    DLOG(INFO) << ModelSafeGroupToString(GetModelSafeGroup())
+        << " worker stops on destruction of its working thread.";
+  }
+
+  if (observer_)
+    observer_->OnWorkerLoopDestroyed(GetModelSafeGroup());
+}
+
 }  // namespace syncer