Cleanup dart to string conversions.

Source/WebCore/bindings/dart/custom/DartHistoryCustom.cpp

 // 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 36 matching lines @@
 {
     DartApiScope dartApiScope;
     Dart_Handle exception = 0;
     {
         History* receiver = DartDOMWrapper::receiver<History>(args);
 
         RefPtr<SerializedScriptValue> data = DartUtilities::dartToSerializedScriptValue(Dart_GetNativeArgument(args, 1), exception);
         if (exception)
             goto fail;
 
-        const ParameterAdapter<String> title(Dart_GetNativeArgument(args, 2));
-        if (!title.conversionSuccessful()) {
-            exception = title.exception();
+        DartStringAdapter title = DartUtilities::dartToString(Dart_GetNativeArgument(args, 2), exception);
+        if (exception)
             goto fail;
-        }
 
         // FIXME: url argument should be optional.
-        const ParameterAdapter<String> url(Dart_GetNativeArgument(args, 3));
-        if (!url.conversionSuccessful()) {
-            exception = url.exception();
+        DartStringAdapter url = DartUtilities::dartToString(Dart_GetNativeArgument(args, 3), exception);
+        if (exception)
             goto fail;
-        }
 
         ExceptionCode ec = 0;
         receiver->stateObjectAdded(data.release(), title, url, stateObjectType, ec);
         if (UNLIKELY(ec)) {
             exception = DartDOMWrapper::exceptionCodeToDartException(ec);
             goto fail;
         }
         return;
     }
 
 fail:
     Dart_ThrowException(exception);
     ASSERT_NOT_REACHED();
 }
 
 void pushStateCallback(Dart_NativeArguments args)
 {
     addStateObjectHelper(args, History::StateObjectPush);
 }
 
 void replaceStateCallback(Dart_NativeArguments args)
 {
     addStateObjectHelper(args, History::StateObjectReplace);
 }
 
 }
 
 }