Cleanup dart to string conversions.

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

Index: Source/WebCore/bindings/dart/custom/DartHTMLInputElementCustom.cpp
diff --git a/Source/WebCore/bindings/dart/custom/DartHTMLInputElementCustom.cpp b/Source/WebCore/bindings/dart/custom/DartHTMLInputElementCustom.cpp
index dd466b494cefa7a07df44b1d0e3fb1eaa2f15b89..413fd598bc9e0981ad63bed4320b3400a53e5d7a 100644
--- a/Source/WebCore/bindings/dart/custom/DartHTMLInputElementCustom.cpp
+++ b/Source/WebCore/bindings/dart/custom/DartHTMLInputElementCustom.cpp
@@ -54,11 +54,9 @@ void setSelectionRangeCallback(Dart_NativeArguments args)
         if (exception)
             goto fail;
 
-        const ParameterAdapter<String> direction(Dart_GetNativeArgument(args, 3));
-        if (!direction.conversionSuccessful()) {
-            exception = direction.exception();
+        DartStringAdapter direction = DartUtilities::dartToString(Dart_GetNativeArgument(args, 3), exception);
+        if (exception)
             goto fail;
-        }
 
         receiver->setSelectionRange(start, end, direction);
         return;
@@ -102,11 +100,9 @@ void selectionDirectionSetter(Dart_NativeArguments args)
             goto fail;
         }
 
-        const ParameterAdapter<String> value(Dart_GetNativeArgument(args, 1));
-        if (!value.conversionSuccessful()) {
-            exception = value.exception();
+        DartStringAdapter value = DartUtilities::dartToString(Dart_GetNativeArgument(args, 1), exception);
+        if (exception)
             goto fail;
-        }
 
         receiver->setSelectionDirection(value);
         return;