More informative error messages for non-Transferables.

Source/bindings/v8/custom/V8MessagePortCustom.cpp

Index: Source/bindings/v8/custom/V8MessagePortCustom.cpp
diff --git a/Source/bindings/v8/custom/V8MessagePortCustom.cpp b/Source/bindings/v8/custom/V8MessagePortCustom.cpp
index cedf23f3274ff44d92382051c786a3a1ce722334..f78dd17211efcc6be29313c948ce8d3c217ec8bb 100644
--- a/Source/bindings/v8/custom/V8MessagePortCustom.cpp
+++ b/Source/bindings/v8/custom/V8MessagePortCustom.cpp
@@ -31,6 +31,7 @@
 #include "config.h"
 #include "V8MessagePort.h"
 
+#include "bindings/v8/ExceptionMessages.h"
 #include "bindings/v8/ExceptionState.h"
 #include "bindings/v8/SerializedScriptValue.h"
 #include "bindings/v8/V8Binding.h"
@@ -46,8 +47,12 @@ void V8MessagePort::postMessageMethodCustom(const v8::FunctionCallbackInfo<v8::V
     MessagePortArray portArray;
     ArrayBufferArray arrayBufferArray;
     if (args.Length() > 1) {
-        if (!extractTransferables(args[1], portArray, arrayBufferArray, args.GetIsolate()))
+        bool notASequence = false;
+        if (!extractTransferables(args[1], portArray, arrayBufferArray, notASequence, args.GetIsolate())) {
+            if (notASequence)
+                throwTypeError(ExceptionMessages::failedToExecute("postMessage", "MessagePort", ExceptionMessages::notASequenceType("Second")), args.GetIsolate());
             return;
+        }
     }
     bool didThrow = false;
     RefPtr<SerializedScriptValue> message =