[WIP] bindings: Introduce PropertyBag

Source/bindings/core/v8/custom/V8MessageEventCustom.cpp

Index: Source/bindings/core/v8/custom/V8MessageEventCustom.cpp
diff --git a/Source/bindings/core/v8/custom/V8MessageEventCustom.cpp b/Source/bindings/core/v8/custom/V8MessageEventCustom.cpp
index 8bc5ad18bd0140646cdf2beac519801f9a6ab22f..52b0de23666c93516a82c7cb68550f4136e50e4a 100644
--- a/Source/bindings/core/v8/custom/V8MessageEventCustom.cpp
+++ b/Source/bindings/core/v8/custom/V8MessageEventCustom.cpp
@@ -114,11 +114,12 @@ void V8MessageEvent::initMessageEventMethodCustom(const v8::FunctionCallbackInfo
     LocalDOMWindow* sourceArg = toDOMWindow(info[6], info.GetIsolate());
     OwnPtrWillBeRawPtr<MessagePortArray> portArray = nullptr;
     const int portArrayIndex = 7;
+
     if (!isUndefinedOrNull(info[portArrayIndex])) {
+        ExceptionState exceptionState(ExceptionState::ExecutionContext, "initMessageEvent", info.Holder(), info.GetIsolate());
         portArray = adoptPtrWillBeNoop(new MessagePortArray);
-        bool success = false;
-        *portArray = toRefPtrWillBeMemberNativeArray<MessagePort, V8MessagePort>(info[portArrayIndex], portArrayIndex + 1, info.GetIsolate(), &success);
-        if (!success)
+        *portArray = toRefPtrWillBeMemberNativeArray<MessagePort, V8MessagePort>(info[portArrayIndex], portArrayIndex + 1, info.GetIsolate(), &exceptionState);
+        if (exceptionState.throwIfNeeded())
             return;
     }
     event->initMessageEvent(typeArg, canBubbleArg, cancelableArg, originArg, lastEventIdArg, sourceArg, portArray.release());