Reduce the memory usage of bookmarks storage

components/bookmarks/browser/bookmark_node.cc

 // Copyright 2014 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.
 
 #include "components/bookmarks/browser/bookmark_node.h"
 
 #include <map>
 #include <string>
 
 #include "base/strings/string_util.h"
@@ skipping 105 matching lines @@
   type_ = url_.is_empty() ? FOLDER : URL;
   date_added_ = base::Time::Now();
   favicon_type_ = favicon_base::INVALID_ICON;
   favicon_state_ = INVALID_FAVICON;
   favicon_load_task_id_ = base::CancelableTaskTracker::kBadTaskId;
   meta_info_map_.reset();
   sync_transaction_version_ = kInvalidSyncTransactionVersion;
 }
 
 void BookmarkNode::InvalidateFavicon() {
-  icon_url_ = GURL();
+  icon_url_.reset();
   favicon_ = gfx::Image();
   favicon_type_ = favicon_base::INVALID_ICON;
   favicon_state_ = INVALID_FAVICON;
 }
 
 // BookmarkPermanentNode -------------------------------------------------------
 
 BookmarkPermanentNode::BookmarkPermanentNode(int64_t id)
     : BookmarkNode(id, GURL()), visible_(true) {}
 
 BookmarkPermanentNode::~BookmarkPermanentNode() {
 }
 
 bool BookmarkPermanentNode::IsVisible() const {
   return visible_ || !empty();
 }
 
 }  // namespace bookmarks