[Mac] Reduce jank in the cookie manager by lazily creating child nodes for the UI.

chrome/browser/cocoa/cookie_tree_node.h

 // Copyright (c) 2009 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 <Cocoa/Cocoa.h>
 
 #include "base/scoped_nsobject.h"
 #include "chrome/browser/cookies_tree_model.h"
 
 // This class is used by CookiesWindowController and represents a node in the
 // cookie tree view.
 @interface CocoaCookieTreeNode : NSObject {
   scoped_nsobject<NSString> title_;
   scoped_nsobject<NSMutableArray> children_;
+  // We lazily create children, so we need to know if we are a leaf.
+  BOOL isLeaf_;
 
   // The platform-independent model node.
   CookieTreeNode* treeNode_;  // weak
 
   // These members are only set for true cookie nodes.
   BOOL isCookie_;
   scoped_nsobject<NSString> name_;
   scoped_nsobject<NSString> content_;
   scoped_nsobject<NSString> domain_;
   scoped_nsobject<NSString> path_;
   scoped_nsobject<NSString> sendFor_;
   // Stringifed dates.
   scoped_nsobject<NSString> created_;
   scoped_nsobject<NSString> expires_;
 }
 
 // Designated initializer.
 - (id)initWithNode:(CookieTreeNode*)node;
 
 // Re-sets all the members of the node based on |treeNode_|.
 - (void)rebuild;
 
 - (BOOL)isLeaf;
 
 // Getters.
 - (NSString*)title;
 // |-children| is mutable so that the CookiesTreeModelObserverBridge can
-// operate on the children.
+// operate on the children. Note that this lazily creates children.
 - (NSMutableArray*)children;
 - (TreeModelNode*)treeNode;
 
 // Used only by cookies. Nil for non-cookie nodes.
 - (BOOL)isCookie;
 - (NSString*)name;
 - (NSString*)content;
 - (NSString*)domain;
 - (NSString*)path;
 - (NSString*)sendFor;
 - (NSString*)created;
 - (NSString*)expires;
 
 @end