Make client tag IDs consistent in sync fake server

sync/test/fake_server/fake_server.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 "sync/test/fake_server/fake_server.h"
 
 #include <algorithm>
 #include <limits>
 #include <string>
 #include <vector>
@@ skipping 318 matching lines @@
     if (!DeleteChildren(client_entity.id_string())) {
       return string();
     }
   } else if (GetModelType(client_entity) == syncer::NIGORI) {
     // NIGORI is the only permanent item type that should be updated by the
     // client.
     entity = PermanentEntity::CreateUpdatedNigoriEntity(
         client_entity,
         entities_[client_entity.id_string()]);
   } else if (client_entity.has_client_defined_unique_tag()) {
-    if (entities_.find(client_entity.id_string()) != entities_.end()) {

[pval...(no longer on Chromium), 2014/07/23 23:54:15]

Looking back at this, perhaps I was assuming that client_entity.id_string() was
the client_defined_unique_tag itself.

[rlarocque, 2014/07/24 00:18:39]

Could be.  It's also possible that you implemented it this way because until
recently not all entities were guaranteed to have a ModelType.  Without a
ModelType, it's impossible to derive a unique client tag, so this kind of logic
would have been impossible.

+    const std::string& effective_id =
+        UniqueClientEntity::EffectiveIdForClientTaggedEntity(client_entity);
+    if (entities_.find(effective_id) != entities_.end()) {
       entity = UniqueClientEntity::CreateUpdatedVersion(
-          client_entity,
-          entities_[client_entity.id_string()]);
+          client_entity, entities_[effective_id]);
     } else {
       entity = UniqueClientEntity::CreateNew(client_entity);
     }
   } else {
     // TODO(pvalenzuela): Validate entity's parent ID.
     if (entities_.find(client_entity.id_string()) != entities_.end()) {
       entity = BookmarkEntity::CreateUpdatedVersion(
         client_entity,
         entities_[client_entity.id_string()],
         parent_id);
@@ skipping 167 matching lines @@
 
 void FakeServer::AddObserver(Observer* observer) {
   observers_.AddObserver(observer);
 }
 
 void FakeServer::RemoveObserver(Observer* observer) {
   observers_.RemoveObserver(observer);
 }
 
 }  // namespace fake_server