Cleanup dart to string conversions.

Source/WebCore/bindings/dart/custom/DartDirectoryEntrySyncCustom.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 @@
 
 namespace DartDirectoryEntrySyncInternal {
 
 void getFileCallback(Dart_NativeArguments args)
 {
     DartApiScope dartApiScope;
     Dart_Handle exception = 0;
     {
         DirectoryEntrySync* receiver = DartDOMWrapper::receiver<DirectoryEntrySync>(args);
 
-        ParameterAdapter<String> path(Dart_GetNativeArgument(args, 1), DartUtilities::ConvertNullToDefaultValue);
-        if (!path.conversionSuccessful()) {
-            exception = path.exception();
+        DartStringAdapter path = DartUtilities::dartToStringWithNullCheck(Dart_GetNativeArgument(args, 1), exception);
+        if (exception)
             goto fail;
-        }
 
         RefPtr<WebKitFlags> flags = 0;
         Dart_Handle flagsHandle = Dart_GetNativeArgument(args, 2);
         if (!Dart_IsNull(flagsHandle)) {
             flags = DartUtilities::toWebKitFlags(flagsHandle, exception);
             if (exception)
                 goto fail;
         }
 
         ExceptionCode ec = 0;
@@ skipping 14 matching lines @@
     ASSERT_NOT_REACHED();
 }
 
 void getDirectoryCallback(Dart_NativeArguments args)
 {
     DartApiScope dartApiScope;
     Dart_Handle exception = 0;
     {
         DirectoryEntrySync* receiver = DartDOMWrapper::receiver<DirectoryEntrySync>(args);
 
-        ParameterAdapter<String> path(Dart_GetNativeArgument(args, 1), DartUtilities::ConvertNullToDefaultValue);
-        if (!path.conversionSuccessful()) {
-            exception = path.exception();
+        DartStringAdapter path = DartUtilities::dartToStringWithNullCheck(Dart_GetNativeArgument(args, 1), exception);
+        if (exception)
             goto fail;
-        }
 
         RefPtr<WebKitFlags> flags = 0;
         Dart_Handle flagsHandle = Dart_GetNativeArgument(args, 2);
         if (!Dart_IsNull(flagsHandle)) {
             flags = DartUtilities::toWebKitFlags(flagsHandle, exception);
             if (exception)
                 goto fail;
         }
 
         ExceptionCode ec = 0;
@@ skipping 12 matching lines @@
 fail:
     Dart_ThrowException(exception);
     ASSERT_NOT_REACHED();
 }
 
 }
 
 }
 
 #endif // ENABLE(FILE_SYSTEM)