[sensors] Add a browser test to sanity check ambient light sensor.

device/generic_sensor/platform_sensor_provider_mac.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_mac.h"
 
 #include "base/memory/singleton.h"
 #include "device/generic_sensor/platform_sensor_ambient_light_mac.h"
 
 namespace device {
 
 // static
-PlatformSensorProvider* PlatformSensorProvider::GetInstance() {
-  return PlatformSensorProviderMac::GetInstance();
-}
-
-// static
 PlatformSensorProviderMac* PlatformSensorProviderMac::GetInstance() {
   return base::Singleton<
       PlatformSensorProviderMac,
       base::LeakySingletonTraits<PlatformSensorProviderMac>>::get();
 }
 
 PlatformSensorProviderMac::PlatformSensorProviderMac() = default;
 
 PlatformSensorProviderMac::~PlatformSensorProviderMac() = default;
 
 void PlatformSensorProviderMac::CreateSensorInternal(
     mojom::SensorType type,
     mojo::ScopedSharedBufferMapping mapping,
     const CreateSensorCallback& callback) {
   // Create Sensors here.
   switch (type) {
     case mojom::SensorType::AMBIENT_LIGHT: {
       scoped_refptr<PlatformSensor> sensor =
           new PlatformSensorAmbientLightMac(type, std::move(mapping), this);
       callback.Run(std::move(sensor));
       break;
     }
     default:
       NOTIMPLEMENTED();
       callback.Run(nullptr);
   }
 }
 
 }  // namespace device