Sync: Change Local IDs to GUID based to avoid ID collision

sync/syncable/parent_child_index.cc

 // Copyright (c) 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 "sync/syncable/parent_child_index.h"
 
 #include "base/stl_util.h"
 
 #include "sync/syncable/entry_kernel.h"
 #include "sync/syncable/syncable_id.h"
@@ skipping 16 matching lines @@
     // move all invalid position items to the right.
     return true;
   } else if (!a_pos.IsValid() && b_pos.IsValid()) {
     // TODO(rlarocque): Remove this case.
     // Mirror of the above case.
     return false;
   } else {
     // Position doesn't matter.
     DCHECK(!a->ref(UNIQUE_POSITION).IsValid());
     DCHECK(!b->ref(UNIQUE_POSITION).IsValid());
-    return a->ref(ID) < b->ref(ID);
+    // Sort by META_HANDLE to ensure consistent order for testing.
+    return a->ref(META_HANDLE) < b->ref(META_HANDLE);
   }
 }
 
 ParentChildIndex::ParentChildIndex() {
 }
 
 ParentChildIndex::~ParentChildIndex() {
   STLDeleteContainerPairSecondPointers(
       parent_children_map_.begin(), parent_children_map_.end());
 }
@@ skipping 114 matching lines @@
 }
 
 const Id& ParentChildIndex::GetModelTypeRootId(ModelType model_type) const {
   // TODO(stanisc): Review whether this approach is reliable enough.
   // Should this method simply enumerate children of root node ("r") instead?
   return model_type_root_ids_[model_type];
 }
 
 }  // namespace syncable
 }  // namespace syncer