ThreadWatcher: fix use-after-free 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..aa2046f30a23628d984633b9f48918730d4752fd 100644
--- a/chrome/browser/metrics/thread_watcher.h
+++ b/chrome/browser/metrics/thread_watcher.h
@@ -78,10 +78,10 @@ class ThreadWatcher {
   // base::Bind supports methods with up to 6 parameters. WatchingParams is used
   // as a workaround that limitation for invoking ThreadWatcher::StartWatching.
   struct WatchingParams {
-    const content::BrowserThread::ID& thread_id;
-    const std::string& thread_name;
-    const base::TimeDelta& sleep_time;
-    const base::TimeDelta& unresponsive_time;
+    content::BrowserThread::ID thread_id;
+    std::string thread_name;
+    base::TimeDelta sleep_time;
+    base::TimeDelta unresponsive_time;
     uint32_t unresponsive_threshold;
     bool crash_on_hang;
     uint32_t live_threads_threshold;