Make client tag IDs consistent in sync fake server

sync/test/fake_server/fake_server_entity.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_entity.h"
 
 #include <limits>
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/guid.h"
 #include "base/logging.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "net/base/net_errors.h"
 #include "net/http/http_status_code.h"
 #include "sync/internal_api/public/base/model_type.h"
 #include "sync/protocol/sync.pb.h"
 
 using std::string;
 using std::vector;
 
 using syncer::ModelType;
 
 // The separator used when formatting IDs.
-const char kIdSeparator[] = "/";
+//
+// We chose the underscore character because it doesn't conflict with the
+// special characters used by base/base64.h's encoding, which is also used in
+// the construction of some IDs.
+const char kIdSeparator[] = "_";
 
 namespace fake_server {
 
 FakeServerEntity::~FakeServerEntity() { }
 
 const std::string& FakeServerEntity::GetId() const {
   return id_;
 }
 
 ModelType FakeServerEntity::GetModelType() const {
@@ skipping 57 matching lines @@
   sync_entity->set_id_string(id_);
   sync_entity->set_version(version_);
   sync_entity->set_name(name_);
 
   // Data via accessors
   sync_entity->set_deleted(IsDeleted());
   sync_entity->set_folder(IsFolder());
 }
 
 }  // namespace fake_server