Minor cleanup in worker code
        https://bugs.webkit.org/show_bug.cgi?id=112455

        Reviewed by Anders Carlsson.

        - Added OVERRIDE keywords.
        - Toned down FIXMEs about single MessagePort versions of functions. It's not a given
        that we'll want to get rid of them even when implementing array versions.
        - Explicitly marked virtual destructors as virtual.

        * dom/MessageEvent.cpp:
        * dom/MessageEvent.h:
        * workers/Worker.cpp:
        * workers/Worker.h:
        Removed an unused version of postMessage() that took no MessagePorts. This makes
        it less confusing why MessagePortArray is passed by pointer, and not by reference.

        * workers/DedicatedWorkerContext.cpp:
        (WebCore::DedicatedWorkerContext::~DedicatedWorkerContext):
        * workers/DedicatedWorkerContext.h:
        Added a destructor instead of an implicit one.
        Removed an unused version of postMessage() that took no MessagePorts.

        * workers/SharedWorker.h: Removed an unused virtual function (thank you OVERRIDE!)

        * dom/MessagePort.cpp:
        * dom/MessagePort.h:
        * loader/WorkerThreadableLoader.h:
        * page/DOMWindow.h:
        * workers/AbstractWorker.h:
        * workers/DedicatedWorkerThread.h:
        * workers/SharedWorkerContext.h:
        * workers/SharedWorkerThread.h:
        * workers/WorkerContext.h:
        * workers/WorkerMessagingProxy.h:
        * workers/WorkerObjectProxy.h:
        * workers/WorkerScriptLoader.h:



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@145930 268f45cc-cd09-0410-ab3c-d52691b4dbfc