Add |notify_client_on_reading_change| flag to sensor configuration

device/generic_sensor/sensor_impl.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/sensor_impl.h"
 
 #include <utility>
 
 #include "mojo/public/cpp/bindings/strong_binding.h"
 
 namespace device {
 
 SensorImpl::SensorImpl(scoped_refptr<PlatformSensor> sensor)
-    : sensor_(std::move(sensor)), suspended_(false) {
+    : sensor_(std::move(sensor)),
+      suspended_(false),
+      notify_client_on_reading_change_count_(0) {
   sensor_->AddClient(this);
 }
 
 SensorImpl::~SensorImpl() {
   sensor_->RemoveClient(this);
 }
 
 mojom::SensorClientRequest SensorImpl::GetClient() {
   return mojo::MakeRequest(&client_);
 }
 
 void SensorImpl::AddConfiguration(
     const PlatformSensorConfiguration& configuration,
     AddConfigurationCallback callback) {
+  if (configuration.notify_client_on_reading_change())
+    ++notify_client_on_reading_change_count_;

[Reilly Grant (use Gerrit), 2017/06/09 18:03:39]

This field should only be updated if the sensor accepts the new configuration by
returning true from StartListening.

[juncai, 2017/06/09 19:00:51]

Done.

   // TODO(Mikhail): To avoid overflowing browser by repeated AddConfigs
   // (maybe limit the number of configs per client).
   std::move(callback).Run(sensor_->StartListening(this, configuration));
 }
 
 void SensorImpl::GetDefaultConfiguration(
     GetDefaultConfigurationCallback callback) {
   std::move(callback).Run(sensor_->GetDefaultConfiguration());
 }
 
 void SensorImpl::RemoveConfiguration(
     const PlatformSensorConfiguration& configuration,
     RemoveConfigurationCallback callback) {
+  if (configuration.notify_client_on_reading_change())
+    --notify_client_on_reading_change_count_;
   std::move(callback).Run(sensor_->StopListening(this, configuration));
 }
 
 void SensorImpl::Suspend() {
   suspended_ = true;
   sensor_->UpdateSensor();
 }
 
 void SensorImpl::Resume() {
   suspended_ = false;
   sensor_->UpdateSensor();
 }
 
 void SensorImpl::OnSensorReadingChanged() {
   DCHECK(!suspended_);
-  if (client_)
+  if (client_ && notify_client_on_reading_change_count_ > 0)
     client_->SensorReadingChanged();
 }
 
 void SensorImpl::OnSensorError() {
   DCHECK(!suspended_);
   if (client_)
     client_->RaiseError();
 }
 
 bool SensorImpl::IsNotificationSuspended() {
   return suspended_;
 }
 
 }  // namespace device