Remove implicit conversions from scoped_refptr to T* in media/

This patch was generated by running the rewrite_scoped_refptr clang tool
on a Mac build.

BUG=110610

Review URL: https://codereview.chromium.org/584103002

Cr-Commit-Position: refs/heads/master@{#295837}

media/video/capture/mac/video_capture_device_factory_mac.mm

@@ -173,7 +173,9 @@ void VideoCaptureDeviceFactoryMac::EnumerateDeviceNames(const base::Callback<
     callback.Run(device_names.Pass());
   } else {
     DVLOG(1) << "Enumerating video capture devices using QTKit";
-    base::PostTaskAndReplyWithResult(ui_task_runner_, FROM_HERE,
+    base::PostTaskAndReplyWithResult(
+        ui_task_runner_.get(),
+        FROM_HERE,
         base::Bind(&EnumerateDevicesUsingQTKit),
         base::Bind(&RunDevicesEnumeratedCallback, callback));
   }