[sensors] PlatformSensorProvider implementations are notified when there are no sensor instances

device/generic_sensor/fake_platform_sensor_provider.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 "base/memory/singleton.h"
 
 #include "device/generic_sensor/fake_platform_sensor.h"
 #include "device/generic_sensor/fake_platform_sensor_provider.h"
 
 namespace device {
 
-// static
-FakePlatformSensorProvider* FakePlatformSensorProvider::GetInstance() {
-  return base::Singleton<
-      FakePlatformSensorProvider,
-      base::LeakySingletonTraits<FakePlatformSensorProvider>>::get();
-}
-
 FakePlatformSensorProvider::FakePlatformSensorProvider() = default;
 
 FakePlatformSensorProvider::~FakePlatformSensorProvider() = default;
 
 void FakePlatformSensorProvider::CreateSensorInternal(
     mojom::SensorType type,
     mojo::ScopedSharedBufferMapping mapping,
     const CreateSensorCallback& callback) {
   scoped_refptr<FakePlatformSensor> sensor =
       new FakePlatformSensor(type, std::move(mapping), this);
   callback.Run(std::move(sensor));
 }
 
 }  // namespace device