InfoBarObserver must handle manager shutdown.

This prevents a DCHECK failure when running infobar browser tests and manually
closing the window with the infobar in it.

BUG=none
TEST=none

Change-Id: Iad50464a5a538d9d6e167f7a2c1a22905902770d
Reviewed-on: https://chromium-review.googlesource.com/991468Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#548170}

chrome/browser/infobars/infobar_observer.cc

@@ -32,6 +32,12 @@ void InfoBarObserver::OnInfoBarReplaced(infobars::InfoBar* old_infobar,
   OnNotified(Type::kInfoBarReplaced);
 }
 
+void InfoBarObserver::OnManagerShuttingDown(infobars::InfoBarManager* manager) {
+  if (run_loop_.running())
+    run_loop_.Quit();
+  infobar_observer_.Remove(manager);
+}
+
 void InfoBarObserver::OnNotified(Type type) {
   if (type == type_)
     run_loop_.Quit();

chrome/browser/infobars/infobar_observer.h

@@ -35,6 +35,7 @@ class InfoBarObserver : public infobars::InfoBarManager::Observer {
   void OnInfoBarRemoved(infobars::InfoBar* infobar, bool animate) override;
   void OnInfoBarReplaced(infobars::InfoBar* old_infobar,
                          infobars::InfoBar* new_infobar) override;
+  void OnManagerShuttingDown(infobars::InfoBarManager* manager) override;
 
   void OnNotified(Type type);