Reland: Add an event to notify accessibility when a permissions bubble gets shown.

ui/views/bubble/bubble_delegate.h

Index: ui/views/bubble/bubble_delegate.h
diff --git a/ui/views/bubble/bubble_delegate.h b/ui/views/bubble/bubble_delegate.h
index 3bc73f8c729d0983f07d044dc78186e48cc472c5..e98250132cf8273009b899041f9c535a12cb0826 100644
--- a/ui/views/bubble/bubble_delegate.h
+++ b/ui/views/bubble/bubble_delegate.h
@@ -22,6 +22,9 @@ class BubbleFrameView;
 
 // BubbleDelegateView creates frame and client views for bubble Widgets.
 // BubbleDelegateView itself is the client's contents view.
+// Note for those adding subclasses, to have your view read in its entirety by

[msw, 2015/04/07 21:36:06]

You can leave this comment with the NotifyAccessibilityEvent block in the
HandleVisibilityChanged impl. Consider rephrasing the comment to something like:
"Fire AX_EVENT_ALERT for bubbles marked as AX_ROLE_ALERT_DIALOG; this instructs
accessibility tools to read the bubble in its entirety, rather than just its
title and initially focused view. See http://crbug.com/474622 for details."

[David Tseng, 2015/04/07 21:50:53]

Done.

+// accessibility tools, set your view to ui::AX_ROLE_ALERT_DIALOG. See
+//http://crbug.com/474622 for further context.
 class VIEWS_EXPORT BubbleDelegateView : public WidgetDelegateView,
                                         public WidgetObserver {
  public: