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

Source/bindings/core/v8/PostMessage.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef PostMessage_h
 #define PostMessage_h
 
 #include "bindings/core/v8/ExceptionState.h"
 #include "bindings/core/v8/SerializedScriptValue.h"
 #include "bindings/core/v8/SerializedScriptValueFactory.h"
 #include "bindings/core/v8/V8Binding.h"
 #include "bindings/core/v8/V8BindingMacros.h"
 #include "core/dom/DOMArrayBuffer.h"
 #include "core/dom/MessagePort.h"
 #include <v8.h>
 
 namespace blink {
 
 class ExecutionContext;
 
 // FIXME: This should be auto-generated by a code generator template.
 template <class Type>
 void postMessageMethodCommon(const char* interfaceName, Type* instance, const v8::FunctionCallbackInfo<v8::Value>& info)
 {
     ExceptionState exceptionState(ExceptionState::ExecutionContext, "postMessage", interfaceName, info.Holder(), info.GetIsolate());
+    if (UNLIKELY(info.Length() < 1)) {
+        setMinimumArityTypeError(exceptionState, 1, info.Length());
+        exceptionState.throwIfNeeded();
+        return;
+    }
     MessagePortArray ports;
     ArrayBufferArray arrayBuffers;
     if (info.Length() > 1) {
         const int transferablesArgIndex = 1;
         if (!SerializedScriptValue::extractTransferables(info.GetIsolate(), info[transferablesArgIndex], transferablesArgIndex, ports, arrayBuffers, exceptionState)) {
             exceptionState.throwIfNeeded();
             return;
         }
     }
     RefPtr<SerializedScriptValue> message = SerializedScriptValueFactory::instance().create(info[0], &ports, &arrayBuffers, exceptionState, info.GetIsolate());
     if (exceptionState.throwIfNeeded())
         return;
     // FIXME: Only pass context/exceptionState if instance really requires it.
     ExecutionContext* context = currentExecutionContext(info.GetIsolate());
     instance->postMessage(context, message.release(), &ports, exceptionState);
     exceptionState.throwIfNeeded();
 }
 
 } // namespace blink
 
 #endif // PostMessage_h