Remove ModelSafeWorker::work_done_or_stopped().

components/sync/driver/glue/browser_thread_model_worker.cc

Index: components/sync/driver/glue/browser_thread_model_worker.cc
diff --git a/components/sync/driver/glue/browser_thread_model_worker.cc b/components/sync/driver/glue/browser_thread_model_worker.cc
index 2b77c03a4e4c45a6fb0c754179d414c4b4ffe775..e8245379fd677cf5d2e7ac6f1558fc5f9febae38 100644
--- a/components/sync/driver/glue/browser_thread_model_worker.cc
+++ b/components/sync/driver/glue/browser_thread_model_worker.cc
@@ -27,15 +27,23 @@ SyncerError BrowserThreadModelWorker::DoWorkAndWaitUntilDoneImpl(
     return work.Run();
   }
 
+  // Signaled when the task is deleted, i.e. after it runs or when it is
+  // abandonned.
+  base::WaitableEvent work_done_or_abandonned(
+      base::WaitableEvent::ResetPolicy::AUTOMATIC,
+      base::WaitableEvent::InitialState::NOT_SIGNALED);
+
   if (!runner_->PostTask(
           FROM_HERE,
           base::Bind(&BrowserThreadModelWorker::CallDoWorkAndSignalTask, this,
-                     work, work_done_or_stopped(), &error))) {
+                     work, base::Passed(syncer::SignalEventOnDelete(
+                               &work_done_or_abandonned)),
+                     &error))) {
     DLOG(WARNING) << "Failed to post task to runner " << runner_;
     error = CANNOT_DO_WORK;
     return error;
   }
-  work_done_or_stopped()->Wait();
+  work_done_or_abandonned.Wait();
   return error;
 }
 
@@ -55,13 +63,14 @@ void BrowserThreadModelWorker::RegisterForLoopDestruction() {
   }
 }
 
-void BrowserThreadModelWorker::CallDoWorkAndSignalTask(const WorkCallback& work,
-                                                       WaitableEvent* done,
-                                                       SyncerError* error) {
+void BrowserThreadModelWorker::CallDoWorkAndSignalTask(
+    const WorkCallback& work,
+    syncer::SignalEventOnDelete signal_event_on_delete,
+    SyncerError* error) {
   DCHECK(runner_->BelongsToCurrentThread());
   if (!IsStopped())
     *error = work.Run();
-  done->Signal();
+  // The event in |signal_event_on_delete| is signaled at the end of this scope.
 }
 
 }  // namespace syncer