[sensors](CrOS/Linux) Implement Sensor device manager for sensors

device/generic_sensor/platform_sensor_provider_base.cc

Index: device/generic_sensor/platform_sensor_provider_base.cc
diff --git a/device/generic_sensor/platform_sensor_provider_base.cc b/device/generic_sensor/platform_sensor_provider_base.cc
index c3f30ceb648966f50954ee5717d6e42ac4686551..135dd1e3d6f3e58bbb193fa5eb8bce76ec8bdffc 100644
--- a/device/generic_sensor/platform_sensor_provider_base.cc
+++ b/device/generic_sensor/platform_sensor_provider_base.cc
@@ -32,8 +32,7 @@ void PlatformSensorProviderBase::CreateSensor(
     return;
   }
 
-  mojo::ScopedSharedBufferMapping mapping = shared_buffer_handle_->MapAtOffset(
-      kReadingBufferSize, SensorReadingSharedBuffer::GetOffset(type));
+  mojo::ScopedSharedBufferMapping mapping = GetScopedSharedBufferMapping(type);
   if (!mapping) {
     callback.Run(nullptr);
     return;
@@ -78,6 +77,7 @@ void PlatformSensorProviderBase::RemoveSensor(mojom::SensorType type) {
   DCHECK(CalledOnValidThread());
   DCHECK(ContainsKey(sensor_map_, type));
   sensor_map_.erase(type);
+  SensorRemoved(type);
 
   if (sensor_map_.empty()) {
     AllSensorsRemoved();
@@ -117,4 +117,19 @@ void PlatformSensorProviderBase::NotifySensorCreated(
   requests_map_.erase(type);
 }
 
+std::vector<mojom::SensorType> PlatformSensorProviderBase::GetRequestTypes() {

[Mikhail, 2016/12/08 11:15:22]

GetPendingRequestedTypes

+  std::vector<mojom::SensorType> request_types;
+  for (auto const& entry : requests_map_)
+    request_types.push_back(entry.first);
+  return request_types;
+}
+
+mojo::ScopedSharedBufferMapping
+PlatformSensorProviderBase::GetScopedSharedBufferMapping(
+    mojom::SensorType type) {
+  mojo::ScopedSharedBufferMapping mapping = shared_buffer_handle_->MapAtOffset(

[Mikhail, 2016/12/08 11:15:22]

this should not be called several times, map once and then return stored mapping

[maksims (do not use this acc), 2016/12/08 18:39:17]

But it does not actually overwrite existing mapping.
The call chain is the following.

PlatformSensorBase calls CreateSensorInternal with mapping as a parameter. When
CreateSensorInternal is invoked in PlatformSensorProviderLinux, it checks if it
can create a sensor (if enumeration is ready). If not, mapping is just lost, not
saved or used. Then, when enumeration becomes ready, mapping is recreated
according to pending requests for certain type. MapAtOffset is called only once
for each type of sensor.

+      kReadingBufferSize, SensorReadingSharedBuffer::GetOffset(type));
+  return mapping;
+}
+
 }  // namespace device