Cleanup dart to string conversions.

Source/WebCore/bindings/dart/custom/DartCanvasRenderingContext2DCustom.cpp

Index: Source/WebCore/bindings/dart/custom/DartCanvasRenderingContext2DCustom.cpp
diff --git a/Source/WebCore/bindings/dart/custom/DartCanvasRenderingContext2DCustom.cpp b/Source/WebCore/bindings/dart/custom/DartCanvasRenderingContext2DCustom.cpp
index 6f1566289202a1c19fa9fad2e6c437af1083a1ad..85c9cea399d061a7cb83f382cc88d23b32b7b99f 100644
--- a/Source/WebCore/bindings/dart/custom/DartCanvasRenderingContext2DCustom.cpp
+++ b/Source/WebCore/bindings/dart/custom/DartCanvasRenderingContext2DCustom.cpp
@@ -97,11 +97,9 @@ void strokeStyleSetter(Dart_NativeArguments args)
 
         Dart_Handle arg = Dart_GetNativeArgument(args, 1);
         if (Dart_IsString(arg)) {
-            const ParameterAdapter<String> color(Dart_GetNativeArgument(args, 1));
-            if (!color.conversionSuccessful()) {
-                exception = color.exception();
+            DartStringAdapter color = DartUtilities::dartToString(Dart_GetNativeArgument(args, 1), exception);
+            if (exception)
                 goto fail;
-            }
 
             receiver->setStrokeColor(color);
             return;
@@ -138,11 +136,9 @@ void fillStyleSetter(Dart_NativeArguments args)
 
         Dart_Handle arg = Dart_GetNativeArgument(args, 1);
         if (Dart_IsString(arg)) {
-            const ParameterAdapter<String> color(arg);
-            if (!color.conversionSuccessful()) {
-                exception = color.exception();
+            DartStringAdapter color = DartUtilities::dartToString(arg, exception);
+            if (exception)
                 goto fail;
-            }
 
             receiver->setFillColor(color);
             return;