Revert of Fix memory leak in ThreadWatcher.

chrome/browser/metrics/thread_watcher.cc

Index: chrome/browser/metrics/thread_watcher.cc
diff --git a/chrome/browser/metrics/thread_watcher.cc b/chrome/browser/metrics/thread_watcher.cc
index 1b81d61c2e70059677937b5db3c0ada2b25dc29d..84a00ae4e45f32c74fe06ff11da31ca4f7e64500 100644
--- a/chrome/browser/metrics/thread_watcher.cc
+++ b/chrome/browser/metrics/thread_watcher.cc
@@ -79,11 +79,12 @@
   DCHECK(WatchDogThread::CurrentlyOnWatchDogThread());
 
   // Create a new thread watcher object for the given thread and activate it.
-  std::unique_ptr<ThreadWatcher> watcher(new ThreadWatcher(params));
-
+  ThreadWatcher* watcher = new ThreadWatcher(params);
+
+  DCHECK(watcher);
   // If we couldn't register the thread watcher object, we are shutting down,
-  // so don't activate thread watching.
-  if (!ThreadWatcherList::Register(std::move(watcher)))
+  // then don't activate thread watching.
+  if (!ThreadWatcherList::IsRegistered(params.thread_id))
     return;
   watcher->ActivateThreadWatching();
 }
@@ -223,6 +224,7 @@
 
 void ThreadWatcher::Initialize() {
   DCHECK(WatchDogThread::CurrentlyOnWatchDogThread());
+  ThreadWatcherList::Register(this);
 
   const std::string response_time_histogram_name =
       "ThreadWatcher.ResponseTime." + thread_name_;
@@ -380,14 +382,18 @@
 }
 
 // static
-bool ThreadWatcherList::Register(std::unique_ptr<ThreadWatcher> watcher) {
+void ThreadWatcherList::Register(ThreadWatcher* watcher) {
   DCHECK(WatchDogThread::CurrentlyOnWatchDogThread());
   if (!g_thread_watcher_list_)
-    return false;
-  content::BrowserThread::ID thread_id = watcher->thread_id();
-  DCHECK(g_thread_watcher_list_->registered_.count(thread_id) == 0);
-  g_thread_watcher_list_->registered_[thread_id] = watcher.release();
-  return true;
+    return;
+  DCHECK(!g_thread_watcher_list_->Find(watcher->thread_id()));
+  g_thread_watcher_list_->registered_[watcher->thread_id()] = watcher;
+}
+
+// static
+bool ThreadWatcherList::IsRegistered(const BrowserThread::ID thread_id) {
+  DCHECK(WatchDogThread::CurrentlyOnWatchDogThread());
+  return nullptr != ThreadWatcherList::Find(thread_id);
 }
 
 // static