Only create Mac bubble closer when the bubble is activated.

BubbleDialogDelegateView observes multiple widgets.  It's possible for the
anchor widget to be activated after the bubble widget has been created but
before it's visible (e.g. for ExtensionPopup).  Ensure we're actually observing
the right widget.

Bug: none
Change-Id: If266fb3ed900f1bd345296f1fb1d37ff1c0eee0e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1531720
Auto-Submit: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Trent Apted <tapted@chromium.org>
Commit-Queue: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#642353}

ui/views/bubble/bubble_dialog_delegate_view.cc

@@ -205,7 +205,7 @@ void BubbleDialogDelegateView::OnWidgetActivationChanged(Widget* widget,
                                                          bool active) {
 #if defined(OS_MACOSX)
   // Install |mac_bubble_closer_| the first time the widget becomes active.
-  if (active && !mac_bubble_closer_ && GetWidget()) {
+  if (widget == GetWidget() && active && !mac_bubble_closer_) {
     mac_bubble_closer_ = std::make_unique<ui::BubbleCloser>(
         GetWidget()->GetNativeWindow().GetNativeNSWindow(),
         base::BindRepeating(&BubbleDialogDelegateView::OnDeactivate,