[Extensions] Don't remove the bookmark drag event router as delegate

chrome/browser/extensions/api/bookmark_manager_private/bookmark_manager_private_api.cc

Index: chrome/browser/extensions/api/bookmark_manager_private/bookmark_manager_private_api.cc
diff --git a/chrome/browser/extensions/api/bookmark_manager_private/bookmark_manager_private_api.cc b/chrome/browser/extensions/api/bookmark_manager_private/bookmark_manager_private_api.cc
index b27b6cd135a4ee1c7c5f2477e5978c8bec6d4838..cc139f9e709fdd6724bc09269314a307f256ff8c 100644
--- a/chrome/browser/extensions/api/bookmark_manager_private/bookmark_manager_private_api.cc
+++ b/chrome/browser/extensions/api/bookmark_manager_private/bookmark_manager_private_api.cc
@@ -291,6 +291,8 @@ BookmarkManagerPrivateDragEventRouter::BookmarkManagerPrivateDragEventRouter(
     : web_contents_(web_contents),
       profile_(
           Profile::FromBrowserContext(web_contents_->GetBrowserContext())) {
+  // We need to guarantee the BookmarkTabHelper is created.
+  BookmarkTabHelper::CreateForWebContents(web_contents_);
   BookmarkTabHelper* bookmark_tab_helper =
       BookmarkTabHelper::FromWebContents(web_contents_);
   bookmark_tab_helper->set_bookmark_drag_delegate(this);
@@ -298,10 +300,8 @@ BookmarkManagerPrivateDragEventRouter::BookmarkManagerPrivateDragEventRouter(
 
 BookmarkManagerPrivateDragEventRouter::
     ~BookmarkManagerPrivateDragEventRouter() {
-  BookmarkTabHelper* bookmark_tab_helper =
-      BookmarkTabHelper::FromWebContents(web_contents_);
-  if (bookmark_tab_helper->bookmark_drag_delegate() == this)
-    bookmark_tab_helper->set_bookmark_drag_delegate(NULL);
+  // No need to remove ourselves as the BookmarkTabHelper's delegate, since they
+  // are both WebContentsUserData and will be deleted at the same time.
 }
 
 void BookmarkManagerPrivateDragEventRouter::MaybeCreateForWebContents(