Bindings: Add ScalarValueString support

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 8fcedbb59864eaf3bca6ab9ab89d929289e99d94..5775b701731e4f516804361de804f81ca022fec8 100644
--- a/Source/bindings/v8/V8Binding.h
+++ b/Source/bindings/v8/V8Binding.h
@@ -528,6 +528,9 @@ inline float toFloat(v8::Local<v8::Value> value)
 // Converts a value to a String, throwing if any code unit is outside 0-255.
 String toByteString(v8::Handle<v8::Value>, ExceptionState&);
 
+// Converts a value to a String, replacing unmatched UTF-16 surrogates with replacement characters.
+String toScalarValueString(v8::Handle<v8::Value>, ExceptionState&);
+
 inline v8::Handle<v8::Boolean> v8Boolean(bool value, v8::Isolate* isolate)
 {
     return value ? v8::True(isolate) : v8::False(isolate);