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

chrome/browser/cocoa/cookie_tree_node.mm

 // Copyright (c) 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 "chrome/browser/cocoa/cookie_tree_node.h"
 
 #include "app/l10n_util_mac.h"
 #import "base/i18n/time_formatting.h"
 #include "base/sys_string_conversions.h"
 #include "grit/generated_resources.h"
 
 @implementation CocoaCookieTreeNode
 
 - (id)initWithNode:(CookieTreeNode*)node {
   if ((self = [super init])) {
     DCHECK(node);
     treeNode_ = node;
-
-    const int childCount = node->GetChildCount();
-    children_.reset([[NSMutableArray alloc] initWithCapacity:childCount]);
-    for (int i = 0; i < childCount; ++i) {
-      CookieTreeNode* child = node->GetChild(i);
-      scoped_nsobject<CocoaCookieTreeNode> childNode(
-          [[CocoaCookieTreeNode alloc] initWithNode:child]);
-      [children_ addObject:childNode.get()];
-    }
+    isLeaf_ = (node->GetChildCount() == 0);

[John Grabowski, 2010/02/01 07:52:06]

Not sure why there is a need for a local variable here but if you like it then
it's fine.

 
     [self rebuild];
   }
   return self;
 }
 
 - (void)rebuild {
   title_.reset([base::SysWideToNSString(treeNode_->GetTitle()) retain]);
   isCookie_ = NO;
 
@@ skipping 23 matching lines @@
       sendFor_.reset([l10n_util::GetNSStringWithFixup(
           IDS_COOKIES_COOKIE_SENDFOR_SECURE) retain]);
     } else {
       sendFor_.reset([l10n_util::GetNSStringWithFixup(
           IDS_COOKIES_COOKIE_SENDFOR_ANY) retain]);
     }
   }
 }
 
 - (BOOL)isLeaf {
-  return ([children_ count] == 0);
+  return isLeaf_;
 }
 
 - (NSString*)title {
   return title_.get();
 }
 
 - (NSMutableArray*)children {
-  return children_.get();
+  if (!children_.get()) {
+    const int childCount = treeNode_->GetChildCount();
+    children_.reset([[NSMutableArray alloc] initWithCapacity:childCount]);
+    for (int i = 0; i < childCount; ++i) {
+      CookieTreeNode* child = treeNode_->GetChild(i);
+      scoped_nsobject<CocoaCookieTreeNode> childNode(
+          [[CocoaCookieTreeNode alloc] initWithNode:child]);
+      [children_ addObject:childNode.get()];
+    }
+  }
+  return children_.get();    
 }
 
 - (TreeModelNode*)treeNode {
   return treeNode_;
 }
 
 #pragma mark Cookie Accessors
 
 - (BOOL)isCookie {
   return isCookie_;
@@ skipping 21 matching lines @@
 
 - (NSString*)created {
   return created_.get();
 }
 
 - (NSString*)expires {
   return expires_.get();
 }
 
 @end