Implement debugging local unlock keys in chrome://proximity-auth.

components/proximity_auth/cryptauth/cryptauth_device_manager.h

 // Copyright 2015 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 COMPONENTS_PROXIMITY_AUTH_CRYPTAUTH_CRYPTAUTH_DEVICE_MANAGER_H
 #define COMPONENTS_PROXIMITY_AUTH_CRYPTAUTH_CRYPTAUTH_DEVICE_MANAGER_H
 
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
@@ skipping 86 matching lines @@
 
   // Returns true if a device sync attempt is currently in progress.
   bool IsSyncInProgress() const;
 
   // Returns true if the last device sync failed and the manager is now
   // scheduling sync attempts more aggressively to recover. If no enrollment
   // has ever been recorded, then this function will also return true.
   bool IsRecoveringFromFailure() const;
 
   // Returns a list of remote devices that can unlock the user's other devices.
-  const std::vector<cryptauth::ExternalDeviceInfo>& unlock_keys() {
+  const std::vector<cryptauth::ExternalDeviceInfo>& unlock_keys() const {
     return unlock_keys_;
   }
 
  protected:
   // Creates a new SyncScheduler instance. Exposed for testing.
   virtual scoped_ptr<SyncScheduler> CreateSyncScheduler();
 
  private:
   // CryptAuthGCMManager::Observer:
   void OnResyncMessage() override;
@@ skipping 42 matching lines @@
   base::ObserverList<Observer> observers_;
 
   base::WeakPtrFactory<CryptAuthDeviceManager> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(CryptAuthDeviceManager);
 };
 
 }  // namespace proximity_auth
 
 #endif  // COMPONENTS_PROXIMITY_CRYPTAUTH_CRYPTAUTH_DEVICE_MANAGER_H