[EasyUnlock] Reduce RSSI threshold to -70.

components/proximity_auth/proximity_monitor_impl.cc

 // 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.
 
 #include "components/proximity_auth/proximity_monitor_impl.h"
 
 #include <math.h>
 #include <utility>
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/time/tick_clock.h"
 #include "base/time/time.h"
 #include "components/proximity_auth/logging/logging.h"
 #include "components/proximity_auth/metrics.h"
 #include "components/proximity_auth/proximity_monitor_observer.h"
 #include "device/bluetooth/bluetooth_adapter.h"
 #include "device/bluetooth/bluetooth_adapter_factory.h"
 
 using device::BluetoothDevice;
 
 namespace proximity_auth {
 
 // The time to wait, in milliseconds, between proximity polling iterations.
 const int kPollingTimeoutMs = 250;
 
 // The RSSI threshold below which we consider the remote device to not be in
 // proximity.
-// Tentative value, tested between a cave and Nexus 6 device.
-const int kRssiThreshold = -50;
+// Note: Because this threshold is unconfigurable right now, it is set quite
+// conservatively in order to avoid blocking users.
+const int kRssiThreshold = -70;
 
 // The weight of the most recent RSSI sample.
 const double kRssiSampleWeight = 0.3;
 
 ProximityMonitorImpl::ProximityMonitorImpl(
     cryptauth::Connection* connection,
     std::unique_ptr<base::TickClock> clock)
     : connection_(connection),
       remote_device_is_in_proximity_(false),
       is_active_(false),
@@ skipping 157 matching lines @@
   if (remote_device_is_in_proximity_ != is_now_in_proximity) {
     PA_LOG(INFO) << "[Proximity] Updated proximity state: "
                  << (is_now_in_proximity ? "proximate" : "distant");
     remote_device_is_in_proximity_ = is_now_in_proximity;
     for (auto& observer : observers_)
       observer.OnProximityStateChanged();
   }
 }
 
 }  // namespace proximity_auth