Re-land: bindings: Use MessageEventInit for MessageEvent constructor

Source/core/dom/MessagePort.cpp

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 241 matching lines @@
 
     // Passed-in ports passed validity checks, so we can disentangle them.
     OwnPtr<MessagePortChannelArray> portArray = adoptPtr(new MessagePortChannelArray(ports->size()));
     for (unsigned i = 0; i < ports->size(); ++i)
         (*portArray)[i] = (*ports)[i]->disentangle();
     return portArray.release();
 }
 
 PassOwnPtrWillBeRawPtr<MessagePortArray> MessagePort::entanglePorts(ExecutionContext& context, PassOwnPtr<MessagePortChannelArray> channels)
 {
+    // https://html.spec.whatwg.org/multipage/comms.html#message-ports
+    // |ports| should be an empty array, not null even when there is no ports.
     if (!channels || !channels->size())
-        return nullptr;
+        return adoptPtrWillBeNoop(new MessagePortArray());
 
     OwnPtrWillBeRawPtr<MessagePortArray> portArray = adoptPtrWillBeNoop(new MessagePortArray(channels->size()));
     for (unsigned i = 0; i < channels->size(); ++i) {
         RefPtrWillBeRawPtr<MessagePort> port = MessagePort::create(context);
         port->entangle((*channels)[i].release());
         (*portArray)[i] = port.release();
     }
     return portArray.release();
 }
 
@@ skipping 13 matching lines @@
 {
     ASSERT(executionContext());
     if (!m_scriptStateForConversion) {
         v8::Isolate* isolate = scriptIsolate();
         m_scriptStateForConversion = ScriptState::create(v8::Context::New(isolate), DOMWrapperWorld::create(isolate));
     }
     return m_scriptStateForConversion->context();
 }
 
 } // namespace blink