Fix FormData overloaded append.

Source/bindings/dart/custom/DartFormDataCustom.cpp

Index: Source/bindings/dart/custom/DartFormDataCustom.cpp
diff --git a/Source/bindings/dart/custom/DartFormDataCustom.cpp b/Source/bindings/dart/custom/DartFormDataCustom.cpp
index af79a078da7b8dedd1fb37ddae4a45e849013cd4..79646abec4e9edbf3306fd0f387f7af5b45930f7 100644
--- a/Source/bindings/dart/custom/DartFormDataCustom.cpp
+++ b/Source/bindings/dart/custom/DartFormDataCustom.cpp
@@ -63,45 +63,37 @@ void appendCallback(Dart_NativeArguments args)
     {
         DOMFormData* receiver = DartDOMWrapper::receiver<DOMFormData>(args);
 
-        DartStringAdapter name = DartUtilities::dartToStringWithNullCheck(args, 1, exception);
+        DartStringAdapter name = DartUtilities::dartToString(args, 1, exception);
         if (exception)
             goto fail;
 
-        DartStringAdapter value = DartUtilities::dartToStringWithNullCheck(args, 2, exception);
-        if (exception)
-            goto fail;
-
-        receiver->append(name, value);
+        Dart_Handle arg2 = Dart_GetNativeArgument(args, 2);
 
-        return;
-    }
+        if (Dart_IsString(arg2)) {
+            ASSERT(Dart_GetNativeArgumentCount(args) == 3);
 
-fail:
-    Dart_ThrowException(exception);
-    ASSERT_NOT_REACHED();
-}
+            DartStringAdapter value = DartUtilities::dartToString(arg2, exception);
+            if (exception)
+                goto fail;
 
-void appendBlobCallback(Dart_NativeArguments args)
-{
-    Dart_Handle exception = 0;
-    {
-        DOMFormData* receiver = DartDOMWrapper::receiver<DOMFormData>(args);
+            receiver->append(name, value);
+            return;
+        }
 
-        DartStringAdapter name = DartUtilities::dartToStringWithNullCheck(args, 1, exception);
+        Blob* blob = DartBlob::toNative(arg2, exception);
         if (exception)
             goto fail;
 
-        Dart_Handle valueHandle = Dart_GetNativeArgument(args, 2);
-        Blob* blob = DartBlob::toNative(valueHandle, exception);
-        if (exception)
-            goto fail;
+        if (Dart_GetNativeArgumentCount(args) == 3) {
+            receiver->append(name, blob);
+            return;
+        }
 
         DartStringAdapter filename = DartUtilities::dartToStringWithNullCheck(args, 3, exception);
         if (exception)
             goto fail;
 
         receiver->append(name, blob, filename);
-
         return;
     }