Add |notify_client_on_reading_change| flag to sensor configuration

device/generic_sensor/sensor_impl.cc

Index: device/generic_sensor/sensor_impl.cc
diff --git a/device/generic_sensor/sensor_impl.cc b/device/generic_sensor/sensor_impl.cc
index 33e9cd0bb2a0f14e81f6cbcdaedfbe5e4c4da948..d29f6d33867a6173f980791181eef32df51484a2 100644
--- a/device/generic_sensor/sensor_impl.cc
+++ b/device/generic_sensor/sensor_impl.cc
@@ -11,7 +11,9 @@
 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);
 }
 
@@ -26,6 +28,8 @@ mojom::SensorClientRequest SensorImpl::GetClient() {
 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));
@@ -39,6 +43,8 @@ void SensorImpl::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));
 }
 
@@ -54,7 +60,7 @@ void SensorImpl::Resume() {
 
 void SensorImpl::OnSensorReadingChanged() {
   DCHECK(!suspended_);
-  if (client_)
+  if (client_ && notify_client_on_reading_change_count_ > 0)
     client_->SensorReadingChanged();
 }