[Sensors] Improvements in shared buffer managing

device/generic_sensor/platform_sensor.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.h"
 
 #include <utility>
 
+#include "base/threading/thread_task_runner_handle.h"
 #include "device/generic_sensor/platform_sensor_provider.h"
 #include "device/generic_sensor/public/cpp/platform_sensor_configuration.h"
 
 namespace device {
 
 PlatformSensor::PlatformSensor(mojom::SensorType type,
                                mojo::ScopedSharedBufferMapping mapping,
                                PlatformSensorProvider* provider)
     : shared_buffer_mapping_(std::move(mapping)),
       type_(type),
@@ skipping 54 matching lines @@
 void PlatformSensor::RemoveClient(Client* client) {
   DCHECK(client);
   clients_.RemoveObserver(client);
   auto client_entry = config_map_.find(client);
   if (client_entry != config_map_.end()) {
     config_map_.erase(client_entry);
     UpdateSensorInternal(config_map_);
   }
 }
 
+void PlatformSensor::UpdateSensorReading(const mojom::SensorReading& reading) {
+  ReadingBuffer* buffer =
+      static_cast<ReadingBuffer*>(shared_buffer_mapping_.get());
+  buffer->seqlock.WriteBegin();
+  buffer->data = reading;
+  buffer->seqlock.WriteEnd();
+}
+
 void PlatformSensor::NotifySensorReadingChanged() {
   using ClientsList = decltype(clients_);
   ClientsList::Iterator it(&clients_);
   Client* client;
   while ((client = it.GetNext()) != nullptr) {
     if (!client->IsNotificationSuspended())
       client->OnSensorReadingChanged();
   }
 }
 
@@ skipping 17 matching lines @@
 
   if (!optimal_configuration) {
     StopSensor();
     return true;
   }
 
   return StartSensor(*optimal_configuration);
 }
 
 }  // namespace device