Reduce the memory usage of bookmarks storage

components/sync_bookmarks/bookmark_change_processor.cc

 // Copyright 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.
 
 #include "components/sync_bookmarks/bookmark_change_processor.h"
 
 #include <stddef.h>
 
 #include <map>
 #include <stack>
@@ skipping 950 matching lines @@
     const BookmarkNode* bookmark_node,
     BookmarkModel* model,
     syncer::WriteNode* sync_node) {
   scoped_refptr<base::RefCountedMemory> favicon_bytes(nullptr);
   EncodeFavicon(bookmark_node, model, &favicon_bytes);
   if (favicon_bytes.get() && favicon_bytes->size()) {
     sync_pb::BookmarkSpecifics updated_specifics(
         sync_node->GetBookmarkSpecifics());
     updated_specifics.set_favicon(favicon_bytes->front(),
                                   favicon_bytes->size());
-    updated_specifics.set_icon_url(bookmark_node->icon_url().spec());
+    updated_specifics.set_icon_url(bookmark_node->icon_url()
+                                       ? bookmark_node->icon_url()->spec()
+                                       : std::string());
     sync_node->SetBookmarkSpecifics(updated_specifics);
   }
 }
 
 bool BookmarkChangeProcessor::CanSyncNode(const BookmarkNode* node) {
   return bookmark_model_->client()->CanSyncNode(node);
 }
 
 }  // namespace sync_bookmarks