ObserverList::HasObserver now takes a const pointer.

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"
@@ skipping 79 matching lines @@
   // Simple getters.
   UpdateHandlerMap* update_handler_map();
   CommitContributorMap* commit_contributor_map();
   DirectoryTypeDebugInfoEmitterMap* directory_type_debug_info_emitter_map();
 
   void RegisterDirectoryTypeDebugInfoObserver(
       syncer::TypeDebugInfoObserver* observer);
   void UnregisterDirectoryTypeDebugInfoObserver(
       syncer::TypeDebugInfoObserver* observer);
   bool HasDirectoryTypeDebugInfoObserver(
-      syncer::TypeDebugInfoObserver* observer);
+      const syncer::TypeDebugInfoObserver* observer) const;
   void RequestEmitDebugInfo();
 
   base::WeakPtr<SyncContext> AsWeakPtr();
 
  private:
   void OnEncryptionStateChanged();
 
   ModelTypeSet GetEnabledNonBlockingTypes() const;
   ModelTypeSet GetEnabledDirectoryTypes() const;
 
@@ skipping 45 matching lines @@
   ObserverList<TypeDebugInfoObserver> type_debug_info_observers_;
 
   base::WeakPtrFactory<ModelTypeRegistry> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ModelTypeRegistry);
 };
 
 }  // namespace syncer
 
 #endif // SYNC_ENGINE_MODEL_TYPE_REGISTRY_H_