Remove implicit conversions from scoped_refptr to T* in athena

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

BUG=110610

Review URL: https://codereview.chromium.org/571093003

Cr-Commit-Position: refs/heads/master@{#294888}

athena/system/orientation_controller.cc

@@ -76,7 +76,7 @@ OrientationController::~OrientationController() {
 }
 
 void OrientationController::Shutdown() {
-  CHECK(file_task_runner_);
+  CHECK(file_task_runner_.get());
   StopListening();
   file_task_runner_->PostTask(
       FROM_HERE,