[Mac] Fix BMB chevron button being black on Chrome open.

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

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "chrome/browser/ui/cocoa/bookmarks/bookmark_bar_controller.h"
 
 #include <stddef.h>
 
 #include "base/mac/bundle_locations.h"
 #include "base/mac/sdk_forward_declarations.h"
@@ skipping 847 matching lines @@
 
 // Configure the off-the-side button (e.g. specify the node range,
 // check if we should enable or disable it, etc).
 - (void)configureOffTheSideButtonContentsAndVisibility {
   [[offTheSideButton_ cell] setStartingChildIndex:displayedButtonCount_];
   [[offTheSideButton_ cell]
    setBookmarkNode:bookmarkModel_->bookmark_bar_node()];
   int bookmarkChildren = bookmarkModel_->bookmark_bar_node()->child_count();
   if (bookmarkChildren > displayedButtonCount_) {
     [offTheSideButton_ setHidden:NO];
+    // Set the off the side button as needing re-display. This is needed to
+    // avoid the button being shown with a black background the first time
+    // it's displayed. See https://codereview.chromium.org/1630453002/ for
+    // more context.
+    [offTheSideButton_ setNeedsDisplay:YES];
   } else {
     // If we just deleted the last item in an off-the-side menu so the
     // button will be going away, make sure the menu goes away.
     if (folderController_ &&
         ([folderController_ parentButton] == offTheSideButton_))
       [self closeAllBookmarkFolders];
     // (And hide the button, too.)
     [offTheSideButton_ setHidden:YES];
   }
 }
@@ skipping 2062 matching lines @@
 - (id<BookmarkButtonControllerProtocol>)controllerForNode:
     (const BookmarkNode*)node {
   // See if it's in the bar, then if it is in the hierarchy of visible
   // folder menus.
   if (bookmarkModel_->bookmark_bar_node() == node)
     return self;
   return [folderController_ controllerForNode:node];
 }
 
 @end