Manual fixups for scoped_refptr operator T* removal in base/

BUG=110610

Review URL: https://codereview.chromium.org/511153002

Cr-Commit-Position: refs/heads/master@{#292429}


CrOS-Libchrome-Original-Commit: 077d1b2059778413e7b10db4fe9f248370136edd
diff --git a/base/test/thread_test_helper.h b/base/test/thread_test_helper.h
index 9521de6..f6817b5 100644
--- a/base/test/thread_test_helper.h
+++ b/base/test/thread_test_helper.h
@@ -18,7 +18,8 @@
 // until all pending tasks on a given thread have been executed.
 class ThreadTestHelper : public RefCountedThreadSafe<ThreadTestHelper> {
  public:
-  explicit ThreadTestHelper(MessageLoopProxy* target_thread);
+  explicit ThreadTestHelper(
+      const scoped_refptr<MessageLoopProxy>& target_thread);
 
   // True if RunTest() was successfully executed on the target thread.
   bool Run() WARN_UNUSED_RESULT;