Cleanup dart to string conversions.

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

Index: Source/WebCore/bindings/dart/custom/DartDirectoryEntryCustom.cpp
diff --git a/Source/WebCore/bindings/dart/custom/DartDirectoryEntryCustom.cpp b/Source/WebCore/bindings/dart/custom/DartDirectoryEntryCustom.cpp
index 08c53932d2b555c34447a14c8e38ca07e5a12640..48b4656021339552d63c8ac5aac6f7682e8a6b8a 100644
--- a/Source/WebCore/bindings/dart/custom/DartDirectoryEntryCustom.cpp
+++ b/Source/WebCore/bindings/dart/custom/DartDirectoryEntryCustom.cpp
@@ -46,11 +46,9 @@ void getFileCallback(Dart_NativeArguments args)
     {
         DirectoryEntry* receiver = DartDOMWrapper::receiver<DirectoryEntry>(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);
@@ -84,11 +82,9 @@ void getDirectoryCallback(Dart_NativeArguments args)
     {
         DirectoryEntry* receiver = DartDOMWrapper::receiver<DirectoryEntry>(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);