Bug 1030707 - Part 2: Replace AutoPushJSContext in DataStoreAddRunnable::MainThreadRun. r=bholley

dom/workers/DataStore.cpp

@@ -285,16 +285,13 @@ protected:
   {
     AssertIsOnMainThread();
 
-    // Get the JSContext for the target window
-    nsCOMPtr<nsIScriptGlobalObject> sgo =
-      do_QueryInterface(static_cast<DOMEventTargetHelper*>
-                        (mBackingStore.get())->GetOwner());
-    MOZ_ASSERT(sgo);
-
-    nsCOMPtr<nsIScriptContext> scriptContext = sgo->GetContext();
-    AutoPushJSContext cx(scriptContext ? scriptContext->GetNativeContext()
-                                       : nsContentUtils::GetSafeJSContext());
-    MOZ_ASSERT(cx);
+    // Initialise an AutoJSAPI with the target window.
+    AutoJSAPI jsapi;
+    if (NS_WARN_IF(!jsapi.Init(mBackingStore->GetParentObject()))) {
+      mRv.Throw(NS_ERROR_UNEXPECTED);
+      return true;
+    }
+    JSContext* cx = jsapi.cx();
 
     JS::Rooted<JS::Value> value(cx);
     if (!mObjBuffer.read(cx, &value)) {