Cleanup dart to string conversions.

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

Index: Source/WebCore/bindings/dart/custom/DartMessageEventCustom.cpp
diff --git a/Source/WebCore/bindings/dart/custom/DartMessageEventCustom.cpp b/Source/WebCore/bindings/dart/custom/DartMessageEventCustom.cpp
index 5ae242e730bf4379667d8ca2b59759b5283709d1..2edbc638c8165925513cb956664e578005b4d53c 100644
--- a/Source/WebCore/bindings/dart/custom/DartMessageEventCustom.cpp
+++ b/Source/WebCore/bindings/dart/custom/DartMessageEventCustom.cpp
@@ -109,11 +109,9 @@ void initMessageEventCallback(Dart_NativeArguments args)
     {
         MessageEvent* receiver = DartDOMWrapper::receiver<MessageEvent>(args);
 
-        const ParameterAdapter<String> typeArg(Dart_GetNativeArgument(args, 1));
-        if (!typeArg.conversionSuccessful()) {
-            exception = typeArg.exception();
+        DartStringAdapter typeArg = DartUtilities::dartToString(Dart_GetNativeArgument(args, 1), exception);
+        if (exception)
             goto fail;
-        }
 
         bool canBubbleArg = DartUtilities::dartToBool(Dart_GetNativeArgument(args, 2), exception);
         if (exception)
@@ -127,17 +125,13 @@ void initMessageEventCallback(Dart_NativeArguments args)
         if (exception)
             goto fail;
 
-        const ParameterAdapter<String> originArg(Dart_GetNativeArgument(args, 5));
-        if (!originArg.conversionSuccessful()) {
-            exception = originArg.exception();
+        DartStringAdapter originArg = DartUtilities::dartToString(Dart_GetNativeArgument(args, 5), exception);
+        if (exception)
             goto fail;
-        }
 
-        const ParameterAdapter<String> lastEventIdArg(Dart_GetNativeArgument(args, 6));
-        if (!lastEventIdArg.conversionSuccessful()) {
-            exception = lastEventIdArg.exception();
+        DartStringAdapter lastEventIdArg = DartUtilities::dartToString(Dart_GetNativeArgument(args, 6), exception);
+        if (exception)
             goto fail;
-        }
 
         DOMWindow* sourceArg = DartDOMWindow::toNative(Dart_GetNativeArgument(args, 7), exception);
         if (exception)