begin messageport, transferable objects, impl

Accept transfer argument for StructuredCloneData::write

Allow structured clone reads to return a boolean

Add Transferable trait

Add basic skeletons to MessagePort

Implement transfer and transfer-receiving steps on MessagePort

Use transfer and transfer_receive in StructuredClone callbacks

Implement MessageChannel

Freeze the array object for the MessageEvent ports attribute

Implement transfer argument on window.postMessage

Use ReentrantMutex instead for MessagePortInternal

Accept origin as a parameter in dispatch_jsval

Fix BorrowMut crash with pending_port_message

Detach port on closure and check for detached during transfer

Enable webmessaging tests

fix webidl

fix

components/script/script_runtime.rs

@@ -115,6 +115,7 @@ pub enum ScriptThreadEventCategory {
     ImageCacheMsg,
     InputEvent,
     NetworkEvent,
+    PortMessage,
     Resize,
     ScriptEvent,
     SetScrollState,