Disarm StartupTimeBomb when it is deleted

chrome/browser/metrics/thread_watcher.cc

Index: chrome/browser/metrics/thread_watcher.cc
===================================================================
--- chrome/browser/metrics/thread_watcher.cc	(revision 111993)
+++ chrome/browser/metrics/thread_watcher.cc	(working copy)
@@ -590,7 +590,8 @@
   BrowserThread::PostTask(
       BrowserThread::UI,
       FROM_HERE,
-      base::Bind(StartupTimeBomb::Disarm));
+      base::Bind(&StartupTimeBomb::Disarm,
+                 base::Unretained(StartupTimeBomb::g_startup_timebomb_)));
 }
 
 // static
@@ -828,9 +829,19 @@
 // StartupTimeBomb methods and members.
 //
 // static
-base::Watchdog* StartupTimeBomb::startup_watchdog_ = NULL;
+StartupTimeBomb* StartupTimeBomb::g_startup_timebomb_ = NULL;
 
-// static
+StartupTimeBomb::StartupTimeBomb() : startup_watchdog_(NULL) {
+  CHECK(!g_startup_timebomb_);
+  g_startup_timebomb_ = this;
+}
+
+StartupTimeBomb::~StartupTimeBomb() {
+  DCHECK(this == g_startup_timebomb_);
+  Disarm();
+  g_startup_timebomb_ = NULL;
+}
+
 void StartupTimeBomb::Arm(const base::TimeDelta& duration) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   DCHECK(!startup_watchdog_);
@@ -838,9 +849,8 @@
   startup_watchdog_->Arm();
 }
 
-// static
 void StartupTimeBomb::Disarm() {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  // This could be disarm'ed during shutdown when we are not on UI thread.
   if (startup_watchdog_) {
     startup_watchdog_->Disarm();
     // Allow the watchdog thread to shutdown on UI. Watchdog thread shutdowns