[Sensors] Clamp given sampling frequency to the minimum supported one

device/generic_sensor/platform_sensor.h

 // 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.
 
 #ifndef DEVICE_GENERIC_SENSOR_PLATFORM_SENSOR_H_
 #define DEVICE_GENERIC_SENSOR_PLATFORM_SENSOR_H_
 
 #include <list>
 #include <map>
 
@@ skipping 30 matching lines @@
   virtual mojom::ReportingMode GetReportingMode() = 0;
   virtual PlatformSensorConfiguration GetDefaultConfiguration() = 0;
 
   // Can be overriden to return the sensor maximum sampling frequency
   // value obtained from the platform if it is available. If platfrom
   // does not provide maximum sampling frequency this method must
   // return default frequency.
   // The default implementation returns default frequency.
   virtual double GetMaximumSupportedFrequency();
 
+  // Can be overriden to return the sensor minimum sampling frequency.
+  // The default implementation returns '1.0 / (60 * 60)', i.e. once per hour.

[Reilly Grant (use Gerrit), 2017/02/22 18:40:15]

This feels somewhat arbitrary but using
std::numeric_limits<double>::denorm_min() would probably cause problems.

[Mikhail, 2017/02/23 12:42:34]

yeah, ideally we should get the actual values from the platform.

+  virtual double GetMinimumSupportedFrequency();
+
   mojom::SensorType GetType() const;
 
   bool StartListening(Client* client,
                       const PlatformSensorConfiguration& config);
   bool StopListening(Client* client, const PlatformSensorConfiguration& config);
 
   void UpdateSensor();
 
   void AddClient(Client*);
   void RemoveClient(Client*);
@@ skipping 36 matching lines @@
   base::ObserverList<Client, true> clients_;
   ConfigMap config_map_;
   PlatformSensorProvider* provider_;
   base::WeakPtrFactory<PlatformSensor> weak_factory_;
   DISALLOW_COPY_AND_ASSIGN(PlatformSensor);
 };
 
 }  // namespace device
 
 #endif  // DEVICE_GENERIC_SENSOR_PLATFORM_SENSOR_H_