Cleanup dart to string conversions.

Source/WebCore/bindings/dart/custom/DartIDBKeyCustom.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 27 matching lines @@
 {
     if (Dart_IsNumber(handle)) {
         // FIXME: NaN support.
         double asDouble = DartUtilities::dartToDouble(handle, exception);
         if (exception)
             return 0;
         return IDBKey::createNumber(asDouble);
     }
 
     if (Dart_IsString(handle)) {
-        RefPtr<StringImpl> asStringImpl = DartUtilities::toStringImpl(handle, DartUtilities::ConvertNone, exception);
+        DartStringAdapter asString = DartUtilities::dartToString(handle, exception);
         if (exception)
             return 0;
-        return IDBKey::createString(asStringImpl);
+        return IDBKey::createString(asString);
     }
 
     // FIXME: Support Date case.
 
     if (Dart_IsList(handle)) {
         // FIXME: Support Array case.
         exception = DART_UNIMPLEMENTED_EXCEPTION();
         return 0;
     }
 
@@ skipping 22 matching lines @@
         return Dart_Null();
     }
 
     ASSERT_NOT_REACHED();
     return Dart_Null();
 }
 
 }
 
 #endif // ENABLE(INDEXED_DATABASE)