gpu: Early return GpuCommandBufferStub::OnWaitSyncPoint() if the sync point is retired.

content/common/gpu/sync_point_manager.cc

Index: content/common/gpu/sync_point_manager.cc
diff --git a/content/common/gpu/sync_point_manager.cc b/content/common/gpu/sync_point_manager.cc
index 917871c4dcb4c9464f1492ac4a9d5d10ac294aa3..0e84e1cb99d41fb111f65c2a2bd50891291a1572 100644
--- a/content/common/gpu/sync_point_manager.cc
+++ b/content/common/gpu/sync_point_manager.cc
@@ -57,4 +57,13 @@ void SyncPointManager::AddSyncPointCallback(uint32 sync_point,
   callback.Run();
 }
 
+bool SyncPointManager::IsSyncPointRetired(uint32 sync_point) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  {
+    base::AutoLock lock(lock_);
+    SyncPointMap::iterator it = sync_point_map_.find(sync_point);
+    return it == sync_point_map_.end();
+  }
+}
+
 }  // namespace content