Asynchronously resolve getAvailability callbacks.

content/renderer/presentation/presentation_dispatcher.cc

Index: content/renderer/presentation/presentation_dispatcher.cc
diff --git a/content/renderer/presentation/presentation_dispatcher.cc b/content/renderer/presentation/presentation_dispatcher.cc
index a0b3125568cfa47217c6424ab470549d34f99c92..e0f857e4f63069ad3f09e923b4536617d81888f6 100644
--- a/content/renderer/presentation/presentation_dispatcher.cc
+++ b/content/renderer/presentation/presentation_dispatcher.cc
@@ -255,8 +255,11 @@ void PresentationDispatcher::getAvailability(
   DCHECK(status);
 
   if (status->listening_state == ListeningState::ACTIVE) {
-    callbacks->onSuccess(status->last_known_availability);
-    delete callbacks;
+    base::ThreadTaskRunnerHandle::Get()->PostTask(
+        FROM_HERE,
+        base::Bind(&blink::WebPresentationAvailabilityCallbacks::onSuccess,
+                   base::Owned(callbacks),
+                   status->last_known_availability));
     return;
   }