views: Make sure the bubble-delegate removes itself from the anchor-widget's observer list.

ui/views/bubble/bubble_delegate.cc

Index: ui/views/bubble/bubble_delegate.cc
diff --git a/ui/views/bubble/bubble_delegate.cc b/ui/views/bubble/bubble_delegate.cc
index f593a1b23e21fe762c086a2ce229c8f447b0181f..b74f04d24069f7beed1231ca5ba6adfed9703ddd 100644
--- a/ui/views/bubble/bubble_delegate.cc
+++ b/ui/views/bubble/bubble_delegate.cc
@@ -167,6 +167,14 @@ BubbleDelegateView* BubbleDelegateView::AsBubbleDelegate() {
   return this;
 }
 
+void BubbleDelegateView::WindowClosing() {
+  if (anchor_widget_) {
+    anchor_widget_->RemoveObserver(this);
+    anchor_widget_ = NULL;
+    anchor_view_ = NULL;
+  }
+}
+
 View* BubbleDelegateView::GetContentsView() {
   return this;
 }