Remove HTMLOutputElementCustom which is no longer needed.

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

 // Copyright 2011, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //    * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
 //    * Redistributions in binary form must reproduce the above
@@ skipping 15 matching lines @@
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #include "config.h"
 
 #if ENABLE(NOTIFICATIONS)
 
 #include "DartHTMLMediaElement.h"
 
+#include "DartMediaController.h"
+
 namespace WebCore {
 
 namespace DartHTMLMediaElementInternal {
 
-void controllerSetter(Dart_NativeArguments)
+void controllerSetter(Dart_NativeArguments args)
 {
-    // FIXME: proper implementation.
-    DART_UNIMPLEMENTED();
+    DartApiScope dartApiScope;
+    Dart_Handle exception = 0;
+    {
+        HTMLMediaElement* receiver = DartDOMWrapper::receiver<HTMLMediaElement>(args);
+        MediaController* controller = DartDOMWrapper::unwrapDartWrapper<DartMediaController>(Dart_GetNativeArgument(args, 1), exception);
+        if (exception)
+            goto fail;
+
+        // 4.8.10.11.2 Media controllers: controller attribute.
+        // On setting, it must first remove the element's mediagroup attribute, if any,
+        receiver->setMediaGroup(String());
+        // and then set the current media controller to the given value.
+        receiver->setController(controller);
+        return;
+    }
+
+fail:
+    Dart_ThrowException(exception);
+    ASSERT_NOT_REACHED();
 }
 
 }
 
 }
 
 #endif // ENABLE(NOTIFICATIONS)