ThreadWatcher: fix use-after-delete bug.

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 6bf8d15cd1fccf0abf0abe431b6906861587f506..79114b5ab1c764972e575aea43c3b98ac3618710 100644
--- a/chrome/browser/metrics/thread_watcher.h
+++ b/chrome/browser/metrics/thread_watcher.h
@@ -626,9 +626,10 @@ class StartupTimeBomb {
   static void DisarmStartupTimeBomb();
 
  private:
-  // Deletes |startup_watchdog_| if it is joinable. If |startup_watchdog_| is
-  // not joinable, then it will post a delayed task to try again.
-  void DeleteStartupWatchdog();
+  // Deletes the watchdog thread if it is joinable; otherwise it posts a delayed
+  // task to try again.
+  static void DeleteStartupWatchdog(const base::PlatformThreadId thread_id,
+                                    base::Watchdog* startup_watchdog);
 
   // The singleton of this class.
   static StartupTimeBomb* g_startup_timebomb_;