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

chrome/browser/cocoa/cookies_window_controller_unittest.mm

 // Copyright (c) 2009-2010 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 "app/tree_model.h"
 #import "base/scoped_nsobject.h"
 #include "base/scoped_ptr.h"
 #include "chrome/browser/cocoa/browser_test_helper.h"
@@ skipping 36 matching lines @@
 // window controller. This leads to errors for |-addObject:| messages. Maybe
 // it's a compiler bug? Or there's something strange happening via swizzling in
 // the test environment? Or did somebody forget to sacrifice a lamb on the new
 // moon? After investigating for long time, the easiest/best solution was to
 // create this hacky secondary getter.
 @interface CocoaCookieTreeNode (UglyHacks)
 - (NSMutableArray*)childs;
 @end
 @implementation CocoaCookieTreeNode (UglyHacks)
 - (NSMutableArray*)childs {
-  return children_.get();
+  return (NSMutableArray*)[self children];
 }
 @end
 
 namespace {
 
 class CookiesWindowControllerTest : public CocoaTest {
  public:
   virtual void SetUp() {
     CocoaTest::SetUp();
     TestingProfile* profile = browser_helper_.profile();
@@ skipping 478 matching lines @@
   [controller_ updateFilter:field];
   EXPECT_EQ(0U, [[[controller_ cocoaTreeModel] childs] count]);
 
   // Search for "aa".
   [field setStringValue:@"aa"];
   [controller_ updateFilter:field];
   EXPECT_EQ(1U, [[[controller_ cocoaTreeModel] childs] count]);
 }
 
 }  // namespace