[Sync] Refactor ModelSafeWorker::DoWorkAndWaitUntilDone() to avoid code duplication.

components/sync/engine/ui_model_worker.cc

Index: components/sync/engine/ui_model_worker.cc
diff --git a/components/sync/engine/ui_model_worker.cc b/components/sync/engine/ui_model_worker.cc
index 77fe9c7799a65db7437df9cc45edf62a0611467c..08cc1a2502bbd09f396b756bc47bd070eca0782b 100644
--- a/components/sync/engine/ui_model_worker.cc
+++ b/components/sync/engine/ui_model_worker.cc
@@ -6,90 +6,11 @@
 
 #include <utility>
 
-#include "base/bind.h"
-#include "base/bind_helpers.h"
-#include "base/callback.h"
-#include "components/sync/base/scoped_event_signal.h"
-
 namespace syncer {
 
-namespace {
-
-class ScopedEventSignalWithWorker {
- public:
-  ScopedEventSignalWithWorker(scoped_refptr<UIModelWorker> ui_model_worker,
-                              base::WaitableEvent* event)
-      : ui_model_worker_(std::move(ui_model_worker)),
-        scoped_event_signal_(event) {}
-
-  ScopedEventSignalWithWorker(ScopedEventSignalWithWorker&&) = default;
-  ScopedEventSignalWithWorker& operator=(ScopedEventSignalWithWorker&&) =
-      default;
-
-  bool IsStopped() const { return ui_model_worker_->IsStopped(); }
-
- private:
-  // This reference prevents the event in |scoped_event_signal_| from being
-  // signaled after being deleted.
-  scoped_refptr<UIModelWorker> ui_model_worker_;
-
-  ScopedEventSignal scoped_event_signal_;
-
-  DISALLOW_COPY_AND_ASSIGN(ScopedEventSignalWithWorker);
-};
-
-void CallDoWorkAndSignalEvent(
-    const WorkCallback& work,
-    ScopedEventSignalWithWorker scoped_event_signal_with_worker,
-    SyncerError* error_info) {
-  if (!scoped_event_signal_with_worker.IsStopped())
-    *error_info = work.Run();
-  // The event in |scoped_event_signal_with_worker| is signaled at the end of
-  // this scope.
-}
-
-}  // namespace
-
 UIModelWorker::UIModelWorker(
     scoped_refptr<base::SingleThreadTaskRunner> ui_thread)
-    : ui_thread_(std::move(ui_thread)),
-      work_done_or_abandoned_(base::WaitableEvent::ResetPolicy::MANUAL,
-                              base::WaitableEvent::InitialState::NOT_SIGNALED),
-      stop_requested_(base::WaitableEvent::ResetPolicy::MANUAL,
-                      base::WaitableEvent::InitialState::NOT_SIGNALED) {
-  sequence_checker_.DetachFromSequence();
-}
-
-SyncerError UIModelWorker::DoWorkAndWaitUntilDoneImpl(
-    const WorkCallback& work) {
-  DCHECK(sequence_checker_.CalledOnValidSequence());
-  DCHECK(!ui_thread_->BelongsToCurrentThread());
-
-  SyncerError error_info;
-  work_done_or_abandoned_.Reset();
-
-  if (!ui_thread_->PostTask(
-          FROM_HERE,
-          base::Bind(&CallDoWorkAndSignalEvent, work,
-                     base::Passed(syncer::ScopedEventSignalWithWorker(
-                         this, &work_done_or_abandoned_)),
-                     &error_info))) {
-    DLOG(WARNING) << "Could not post work to UI loop.";
-    error_info = CANNOT_DO_WORK;
-    return error_info;
-  }
-
-  base::WaitableEvent* events[] = {&work_done_or_abandoned_, &stop_requested_};
-  base::WaitableEvent::WaitMany(events, arraysize(events));
-
-  return error_info;
-}
-
-void UIModelWorker::RequestStop() {
-  DCHECK(ui_thread_->BelongsToCurrentThread());
-  ModelSafeWorker::RequestStop();
-  stop_requested_.Signal();
-}
+    : ui_thread_(std::move(ui_thread)) {}
 
 ModelSafeGroup UIModelWorker::GetModelSafeGroup() {
   return GROUP_UI;
@@ -101,4 +22,8 @@ bool UIModelWorker::IsOnModelThread() {
 
 UIModelWorker::~UIModelWorker() {}
 
+void UIModelWorker::ScheduleWork(base::OnceClosure work) {
+  ui_thread_->PostTask(FROM_HERE, std::move(work));
+}
+
 }  // namespace syncer