Removed NOTIFICATION_BROWSER_CLOSING notification

chrome/browser/ui/browser.cc

Index: chrome/browser/ui/browser.cc
diff --git a/chrome/browser/ui/browser.cc b/chrome/browser/ui/browser.cc
index 832153b86e17201770479a2f4bfa17284c823b52..8682c00804f3af0a46307afe2410fd212ecc8eb6 100644
--- a/chrome/browser/ui/browser.cc
+++ b/chrome/browser/ui/browser.cc
@@ -746,6 +746,8 @@ void Browser::OnWindowClosing() {
   if (tab_restore_service && is_type_tabbed() && tab_strip_model_->count())
     tab_restore_service->BrowserClosing(live_tab_context());
 
+  BrowserList::NotifyBrowserCloseStarted(this);
+
   // TODO(sky): convert session/tab restore to use notification.
   content::NotificationService::current()->Notify(
       chrome::NOTIFICATION_BROWSER_CLOSING,
@@ -2556,7 +2558,11 @@ bool Browser::ShouldHideUIForFullscreen() const {
 }
 
 bool Browser::ShouldStartShutdown() const {
-  return BrowserList::GetInstance()->size() <= 1;
+  DCHECK_GE(BrowserList::GetInstance()->size(),
+            BrowserList::GetInstance()->currently_closing_browsers_count());
+  // Start shutdown process only when closing the last browser.
+  return BrowserList::GetInstance()->size() ==
+         BrowserList::GetInstance()->currently_closing_browsers_count() + 1;

[hashimoto, 2017/04/04 08:54:07]

A browser close can be cancelled.
What happens if a browser close gets cancelled after a shutdown is started?

[Alexey Seren, 2017/04/09 17:51:37]

If browser close is cancelled then browser will be removed from
currently_closing_browsers_ list in following method:
BrowserList::NotifyBrowserCloseCancelled.

Also shutdown state will be reset in BrowserCloseManager::CancelBrowserClose()
method by calling of browser_shutdown::SetTryingToQuit(false). One problem here
is that g_shutdown_type remains unchanged. I have fixed this by setting
g_shutdown_type to NOT_VALID.

 }
 
 bool Browser::MaybeCreateBackgroundContents(