[EasyUnlock] Update ProximityMonitor to only check for RSSI proximity.

components/proximity_auth/proximity_monitor.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_PROXIMITY_MONITOR_H
 #define COMPONENTS_PROXIMITY_AUTH_PROXIMITY_MONITOR_H
 
 #include "components/proximity_auth/proximity_monitor_observer.h"
 
 namespace proximity_auth {
 
 // An interface that is responsible for tracking whether the remote device is
 // sufficiently close to the local device to permit unlocking.
 class ProximityMonitor {
  public:
-  enum class Strategy { NONE, CHECK_RSSI, CHECK_TRANSMIT_POWER };
-
   virtual ~ProximityMonitor() {}
 
   // Activates the proximity monitor. No-op if the proximity monitor is already
   // active.
   virtual void Start() = 0;
 
   // Deactivates the proximity monitor. No-op if the proximity monitor is
   // already inactive.
   virtual void Stop() = 0;
 
-  // Returns the strategy used to determine whether the remote device is in
-  // proximity.
-  virtual Strategy GetStrategy() const = 0;
-
   // Returns |true| iff the remote device is close enough to the local device,
   // given the user's current settings.
   virtual bool IsUnlockAllowed() const = 0;
 
-  // Returns |true| iff the remote device is close enough to the local device,
-  // according to its RSSI measurement.
-  virtual bool IsInRssiRange() const = 0;
-
   // Records the current proximity measurements to UMA. This should be called
   // when the user successfully authenticates using proximity auth.
   virtual void RecordProximityMetricsOnAuthSuccess() = 0;
 
   // Adds an observer.
   virtual void AddObserver(ProximityMonitorObserver* observer) = 0;
 
   // Removes an observer.
   virtual void RemoveObserver(ProximityMonitorObserver* observer) = 0;
 };
 
 }  // namespace proximity_auth
 
 #endif  // COMPONENTS_PROXIMITY_AUTH_PROXIMITY_MONITOR_H