sync: Introduce classes for per-type counters

sync/sessions/model_type_registry.h

 // 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.
 
 #ifndef SYNC_ENGINE_MODEL_TYPE_REGISTRY_H_
 #define SYNC_ENGINE_MODEL_TYPE_REGISTRY_H_
 
 #include <map>
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/scoped_vector.h"
 #include "sync/base/sync_export.h"
 #include "sync/internal_api/public/base/model_type.h"
 #include "sync/internal_api/public/engine/model_safe_worker.h"
+#include "sync/internal_api/public/sessions/type_debug_info_observer.h"
 
 namespace syncer {
 
 namespace syncable {
 class Directory;
 }  // namespace syncable
 
 class CommitContributor;
 class DirectoryCommitContributor;
 class DirectoryUpdateHandler;
@@ skipping 70 matching lines @@
 
   // The known ModelSafeWorkers.
   std::map<ModelSafeGroup, scoped_refptr<ModelSafeWorker> > workers_map_;
 
   // The directory.  Not owned.
   syncable::Directory* directory_;
 
   // The set of enabled directory types.
   ModelTypeSet enabled_directory_types_;
 
+  // The set of observers of per-type debug info.
+  //
+  // Each of the DirectoryTypeDebugInfoEmitters needs such a list.  There's
+  // a lot of them, and their lifetimes are unpredictable, so it makes the
+  // book-keeping easier if we just store the list here.  That way it's
+  // guaranteed to live as long as this sync backend.
+  ObserverList<TypeDebugInfoObserver> type_debug_info_observers_;
+
   DISALLOW_COPY_AND_ASSIGN(ModelTypeRegistry);
 };
 
 }  // namespace syncer
 
 #endif // SYNC_ENGINE_MODEL_TYPE_REGISTRY_H_