[Mac] Refactor bookmark bar controller

chrome/browser/ui/cocoa/bookmarks/bookmark_bar_bridge.mm

Index: chrome/browser/ui/cocoa/bookmarks/bookmark_bar_bridge.mm
diff --git a/chrome/browser/ui/cocoa/bookmarks/bookmark_bar_bridge.mm b/chrome/browser/ui/cocoa/bookmarks/bookmark_bar_bridge.mm
index 16fa24fd9574174d053dc7541365323a6db0e8ee..58811b0d8c467f1110e4065513a3056a7f3d7f06 100644
--- a/chrome/browser/ui/cocoa/bookmarks/bookmark_bar_bridge.mm
+++ b/chrome/browser/ui/cocoa/bookmarks/bookmark_bar_bridge.mm
@@ -51,9 +51,11 @@ void BookmarkBarBridge::BookmarkModelLoaded(BookmarkModel* model,
 }
 
 void BookmarkBarBridge::BookmarkModelBeingDeleted(BookmarkModel* model) {

[Elly Fong-Jones, 2017/03/23 15:40:21]

can this happen in other circumstances than the browser being torn down?

-  [controller_ beingDeleted:model];
   model_->RemoveObserver(this);
   model_ = nullptr;
+  // The browser may be being torn down; little is safe to do.  As an
+  // example, it may not be safe to clear the pasteboard.
+  // http://crbug.com/38665
 }
 
 void BookmarkBarBridge::BookmarkNodeMoved(BookmarkModel* model,