Fix crash on clicking the web notification tray

ui/message_center/views/message_center_bubble.cc

Index: ui/message_center/views/message_center_bubble.cc
diff --git a/ui/message_center/views/message_center_bubble.cc b/ui/message_center/views/message_center_bubble.cc
index c65587b2537f1906159a3772a49b0ae6fc717bdc..dac29a81a4a128ebdc0ad7808ef518ca547f999a 100644
--- a/ui/message_center/views/message_center_bubble.cc
+++ b/ui/message_center/views/message_center_bubble.cc
@@ -107,10 +107,12 @@ void MessageCenterBubble::InitializeContents(
   // |new_bubble_view| actually wants. See crbug.com/169390.
   bubble_view()->Layout();
   UpdateBubbleView();
-  bubble_view()
+  DCHECK(bubble_view()->GetFocusManager());
+  views::View* next_focusable_view = bubble_view()
       ->GetFocusManager()
-      ->GetNextFocusableView(nullptr, nullptr, false, false)
-      ->RequestFocus();
+      ->GetNextFocusableView(nullptr, nullptr, false, false);

[stevenjb, 2016/07/07 16:57:12]

If we are going to DCHECK on bubble_view()->GetFocusManager() we should go ahead
and assign it to a local variable, DCHECK that, then use it here.

[yoshiki, 2016/07/11 18:19:48]

Done.

+  if (next_focusable_view)

[stevenjb, 2016/07/07 16:57:12]

Add a comment explaining why next_focusable_view might be null.

[yoshiki, 2016/07/11 18:19:48]

Done.

+    next_focusable_view->RequestFocus();
 }
 
 void MessageCenterBubble::OnBubbleViewDestroyed() {