[sensors] Add GetDefaultConfiguration() to generic sensor mojo interface.

device/generic_sensor/public/interfaces/sensor.mojom

 // 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.
 
 module device.mojom;
 
 // Types of supported sensors
 enum SensorType {
   FIRST = 1,
   AMBIENT_LIGHT = FIRST,
@@ skipping 17 matching lines @@
 };
 
 struct SensorConfiguration {
   // Requested frequency in Hz (max is 60 Hz).
   double frequency;
   // TODO(shalamov): Add map<string, union> for sensor specific configuration.
 };
 
 // Interface for controlling the Sensor.
 interface Sensor {
+
+  // Requests sensor to provide its default configuration.
+  GetDefaultConfiguration() => (SensorConfiguration configuration);
+
   // Requests sensor to start reading sensor data with specified
   // SensorConfiguration.
   // Sensor holds the list of added configurations and it always polls
   // the platform (and updates the shared buffer) at the maxiumum frequency
   // among the obtained from the stored configurations, so that all clients
   // can have sensor data in time.
   // Returns 'true' if |configuration| was successfully added.
   // Returns 'false' if |configuration| could not be added (is invalid
   // or not supported).
   AddConfiguration(SensorConfiguration configuration) => (bool success);
@@ skipping 21 matching lines @@
 // Interface that client of the Sensor interface must implement to observe
 // sensor reading changes and error conditions.
 interface SensorClient {
   // Signals SensorClient when there is an error.
   RaiseError();
 
   // Signals SensorClient when reading has been changed (only for sensors with
   // ReportingMode::ON_CHANGE).
   SensorReadingChanged();
 };