Restore interpretation of Dart null as undefined in dartToScriptValueWithNullCheck.

Source/bindings/dart/DartUtilities.h

 // Copyright 2011, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //    * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
 //    * Redistributions in binary form must reproduce the above
@@ skipping 516 matching lines @@
     }
     // NOTE: consider revisiting this once situation w/ optional arguments checks
     // in dart:html is clearer.
     // The implementation below will convert null to undefined script value. Which
     // is exactly what is desired if actual value wasn't specified at call site,
     // but is most probably wrong if null was explicitly provided. On more positive
     // side indexed db are converted to Dart null anyway, so it might be tricky
     // to observe from user code.
     static ScriptValue dartToScriptValueWithNullCheck(Dart_Handle handle)
     {
+        if (Dart_IsNull(handle)) {
+            V8ScriptState* scriptState = v8ScriptStateForCurrentIsolate();
+            return ScriptValue(scriptState, v8::Undefined(scriptState->isolate()));

[vsm, 2014/07/01 17:12:52]

Did you consider a DartScriptValue wrapping undefined?  

[rmacnak, 2014/07/01 17:20:02]

Right now a DartScriptValue never has an empty handle, so I considered
interpreting the empty handle as undefined. But this would require special cases
in DartScriptValue toString, toJSON, etc, so I think keeping undefined in V8
land is cleaner.

+        }
         return dartToScriptValue(handle);
     }
     static ScriptValue dartToScriptValueWithNullCheck(Dart_NativeArguments args, int index)
     {
         Dart_Handle object = Dart_GetNativeArgument(args, index);
         return dartToScriptValueWithNullCheck(object);
     }
     static Dart_Handle scriptValueToDart(const ScriptValue&);
     static Dart_Handle scriptValueToDart(const ScriptPromise&);
 
@@ skipping 212 matching lines @@
     timerStop = currentTimeMS();  \
     fprintf(stdout, "%s %.3f ms\n", msg, (timerStop - timerStart));
 #else
 #define DART_START_TIMER()
 #define DART_RECORD_TIMER(msg)
 #endif
 
 } // namespace WebCore
 
 #endif // DartUtilities_h