[sensors](CrOS/Linux) Implement Sensor device manager for sensors

device/generic_sensor/platform_sensor_provider_base.cc

 // Copyright 2016 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 "device/generic_sensor/platform_sensor_provider_base.h"
 
 #include <utility>
 
 #include "base/stl_util.h"
 #include "device/generic_sensor/public/interfaces/sensor_provider.mojom.h"
@@ skipping 60 matching lines @@
 
   shared_buffer_handle_ =
       mojo::SharedBufferHandle::Create(kSharedBufferSizeInBytes);
   return shared_buffer_handle_.is_valid();
 }
 
 void PlatformSensorProviderBase::RemoveSensor(mojom::SensorType type) {
   DCHECK(CalledOnValidThread());
   DCHECK(ContainsKey(sensor_map_, type));
   sensor_map_.erase(type);
+  SensorRemoved(type);
 
   if (sensor_map_.empty()) {
     AllSensorsRemoved();
     shared_buffer_handle_.reset();
   }
 }
 
 mojo::ScopedSharedBufferHandle
 PlatformSensorProviderBase::CloneSharedBufferHandle() {
   DCHECK(CalledOnValidThread());
@@ skipping 20 matching lines @@
   // Inform subscribers about the sensor.
   // |sensor| can be nullptr here.
   auto it = requests_map_.find(type);
   for (auto& callback : it->second)
     callback.Run(sensor);
 
   requests_map_.erase(type);
 }
 
 }  // namespace device