Add ByteString support to IDL bindings

Source/bindings/v8/V8Binding.h

Index: Source/bindings/v8/V8Binding.h
diff --git a/Source/bindings/v8/V8Binding.h b/Source/bindings/v8/V8Binding.h
index 4e093882fb9e78b7b13b8db4ca8340eb4a9426c6..0b6ce7ede7e9acc7dac9fb837b104bb8dbbfb56f 100644
--- a/Source/bindings/v8/V8Binding.h
+++ b/Source/bindings/v8/V8Binding.h
@@ -525,6 +525,9 @@ inline float toFloat(v8::Local<v8::Value> value)
     return static_cast<float>(value->NumberValue());
 }
 
+// Converts a value to a String, throwing if any code unit is outside 0-255.
+String toByteString(v8::Handle<v8::Value>, ExceptionState&);
+
 inline v8::Handle<v8::Boolean> v8Boolean(bool value, v8::Isolate* isolate)
 {
     return value ? v8::True(isolate) : v8::False(isolate);