Revert of Fix memory leak in ThreadWatcher.

chrome/browser/metrics/thread_watcher.h

Index: chrome/browser/metrics/thread_watcher.h
diff --git a/chrome/browser/metrics/thread_watcher.h b/chrome/browser/metrics/thread_watcher.h
index d61a3836c542ebe6605ba4ded2820516259e91d9..6bf8d15cd1fccf0abf0abe431b6906861587f506 100644
--- a/chrome/browser/metrics/thread_watcher.h
+++ b/chrome/browser/metrics/thread_watcher.h
@@ -102,8 +102,6 @@
           live_threads_threshold(live_threads_threshold_in) {}
   };
 
-  virtual ~ThreadWatcher();
-
   // This method starts performing health check on the given |thread_id|. It
   // will create ThreadWatcher object for the given |thread_id|, |thread_name|.
   // |sleep_time| is the wait time between ping messages. |unresponsive_time| is
@@ -145,6 +143,8 @@
   // wait time between ping messages. |unresponsive_time| is the wait time after
   // ping message is sent, to check if we have received pong message or not.
   explicit ThreadWatcher(const WatchingParams& params);
+
+  virtual ~ThreadWatcher();
 
   // This method activates the thread watching which starts ping/pong messaging.
   virtual void ActivateThreadWatching();
@@ -394,8 +394,10 @@
   static void StopWatchingAll();
 
   // Register() stores a pointer to the given ThreadWatcher in a global map.
-  // Returns true if it was successfully registered.
-  static bool Register(std::unique_ptr<ThreadWatcher> watcher);
+  static void Register(ThreadWatcher* watcher);
+
+  // This method returns true if the ThreadWatcher object is registerd.
+  static bool IsRegistered(const content::BrowserThread::ID thread_id);
 
   // This method returns number of responsive and unresponsive watched threads.
   static void GetStatusOfThreads(uint32_t* responding_thread_count,