Have postMessage()s throw TypeError on failed arity checks.

LayoutTests/fast/workers/resources/worker-multi-port.js

 description("This test checks the various use cases around sending multiple ports through Worker.postMessage");
 
 if (window.testRunner) {
     testRunner.dumpAsText();
     testRunner.waitUntilDone();
 }
 
 var channel = new MessageChannel();
 var channel2 = new MessageChannel();
 var channel3 = new MessageChannel();
 var channel4 = new MessageChannel();
 
 var worker = new Worker("resources/worker-thread-multi-port.js");
+worker.postMessage("noargs");
 worker.postMessage("noport");
 worker.postMessage("zero ports", []);
 worker.postMessage("two ports", [channel2.port1, channel2.port2]);
 
 // Now test various failure cases
+shouldThrow("worker.postMessage()");
 shouldThrow('worker.postMessage("null port", [channel3.port1, null, channel3.port2])');
 shouldThrow('worker.postMessage("notAPort", [channel3.port1, {}, channel3.port2])');
 // Should be OK to send channel3.port1/2 (should not have been disentangled by the previous failed calls).
 worker.postMessage("failed ports", [channel3.port1, channel3.port2]);
 
 shouldThrow('worker.postMessage("notAnArray", channel3.port1)')
 shouldThrow('worker.postMessage("notASequence", [{length: 3}])');
 
 worker.postMessage("done", [channel.port2]);
 worker.onmessage = function(event) {
     // Report results from worker thread.
     if (event.data == "done")
         channel.port1.onmessage = done;
     else if (event.data.indexOf("PASS") == 0)
         testPassed(event.data.substring(4));
     else if (event.data.indexOf("FAIL") == 0)
         testFailed(event.data.substring(4));
     else
         testFailed("Unexpected result: " + event.data);
 }
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