Improve TypeError messages from failed array conversions.

Source/bindings/v8/ExceptionMessages.h

Index: Source/bindings/v8/ExceptionMessages.h
diff --git a/Source/bindings/v8/ExceptionMessages.h b/Source/bindings/v8/ExceptionMessages.h
index 440b00920416c1a290bf0fc3c81a25ce94921c53..6bd37d02784c63558a591a38350529916164f700 100644
--- a/Source/bindings/v8/ExceptionMessages.h
+++ b/Source/bindings/v8/ExceptionMessages.h
@@ -43,7 +43,8 @@ public:
     static String failedToSet(const String& property, const String& type, const String& detail);
     static String failedToDelete(const String& property, const String& type, const String& detail);
 
-    static String notASequenceType(const String& argument);
+    static String notASequenceType(int argumentIndex);

[Mike West, 2013/10/24 07:08:54]

`notASequenceType(2)` isn't particularly readable. Perhaps rename this to
'notASequenceTypeAtIndex'? I'm a bit worried that we're otherwise sprinkling
magic numbers through the code that aren't particularly clear.

[sof, 2013/10/24 21:16:41]

Agree with the concern; tidied up the use of constants at the call sites + tried
to improve naming & purpose of this helper. 

+    static String notASequenceType(const String& argument, const String& argumentKind = String());

[Mike West, 2013/10/24 07:08:54]

Is the optionality of the second argument actually used? It looks like you're
calling this with 'property' everywhere. If so, I'd suggest just renaming it to
'notASequenceTypeInProperty' or something similar, and dropping the second
argument.

     static String notEnoughArguments(unsigned expected, unsigned providedleastNumMandatoryParams);
 };