More informative error messages for non-Transferables.

Source/bindings/v8/V8Utilities.h

Index: Source/bindings/v8/V8Utilities.h
diff --git a/Source/bindings/v8/V8Utilities.h b/Source/bindings/v8/V8Utilities.h
index f1e664d5b4d25fe1961b0079326e77b0d9c4d322..6d72e11e730450e2670d1039c3404b0768a52112 100644
--- a/Source/bindings/v8/V8Utilities.h
+++ b/Source/bindings/v8/V8Utilities.h
@@ -58,9 +58,11 @@ namespace WebCore {
 
     // Helper function which pulls the values out of a JS sequence and into a MessagePortArray.
     // Also validates the elements per sections 4.1.13 and 4.1.15 of the WebIDL spec and section 8.3.3
-    // of the HTML5 spec and generates exceptions as appropriate.
+    // of the HTML5 spec and generates exceptions as appropriate. If the supplied argument's type isn't
+    // a JS sequence, a type error is signalled by setting 'notASequence' to true -- the caller
+    // then being responsible for generating a TypeError having a message that fits the context.
     // Returns true if the array was filled, or false if the passed value was not of an appropriate type.
-    bool extractTransferables(v8::Local<v8::Value>, MessagePortArray&, ArrayBufferArray&, v8::Isolate*);
+    bool extractTransferables(v8::Local<v8::Value>, MessagePortArray&, ArrayBufferArray&, bool& notASequence, v8::Isolate*);
     bool getMessagePortArray(v8::Local<v8::Value>, MessagePortArray&, v8::Isolate*);
 
 } // namespace WebCore