Cleanup dart to string conversions.

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

 // Copyright 2012, 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 24 matching lines @@
 
 namespace WebCore {
 
 namespace DartIntentInternal {
 
 void constructorCallback(Dart_NativeArguments args)
 {
     DartApiScope dartApiScope;
     Dart_Handle exception = 0;
     {
-        const ParameterAdapter<String> action(Dart_GetNativeArgument(args, 0));
-        if (!action.conversionSuccessful()) {
-            exception = action.exception();
+        DartStringAdapter action = DartUtilities::dartToString(Dart_GetNativeArgument(args, 0), exception);
+        if (exception)
             goto fail;
-        }
 
-        const ParameterAdapter<String> type(Dart_GetNativeArgument(args, 1));
-        if (!type.conversionSuccessful()) {
-            exception = type.exception();
+        DartStringAdapter type = DartUtilities::dartToString(Dart_GetNativeArgument(args, 1), exception);
+        if (exception)
             goto fail;
-        }
 
         RefPtr<SerializedScriptValue> data;
         if (!Dart_IsNull(Dart_GetNativeArgument(args, 2))) {
             data = DartUtilities::dartToSerializedScriptValue(Dart_GetNativeArgument(args, 2), exception);
             if (exception)
                 goto fail;
         }
 
         MessagePortArray transferList;
         ArrayBufferArray arrayBufferArray;
@@ skipping 15 matching lines @@
 fail:
     Dart_ThrowException(exception);
     ASSERT_NOT_REACHED();
 }
 
 }
 
 }
 
 #endif