[sensors] Ambient light sensor implementation for ChromeOS and Linux.

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 58 matching lines @@
   if (shared_buffer_handle_.is_valid())
     return true;
 
   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);
+  if (ContainsKey(sensor_map_, type))

[Mikhail, 2016/10/11 14:46:47]

why this change is needed?

+    sensor_map_.erase(type);
 
   if (sensor_map_.empty())
     shared_buffer_handle_.reset();
 }
 
 mojo::ScopedSharedBufferHandle
 PlatformSensorProviderBase::CloneSharedBufferHandle() {
   DCHECK(CalledOnValidThread());
   CreateSharedBufferIfNeeded();
   return shared_buffer_handle_->Clone();
@@ skipping 12 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