[sensors] Add Generic Sensor platform unit tests.

device/generic_sensor/platform_sensor.h

Index: device/generic_sensor/platform_sensor.h
diff --git a/device/generic_sensor/platform_sensor.h b/device/generic_sensor/platform_sensor.h
index 0f263804d62197b1ee510ea2785935aa5bfc1fd1..24f945e3b1e718a5a43216769dc63d80ede56dda 100644
--- a/device/generic_sensor/platform_sensor.h
+++ b/device/generic_sensor/platform_sensor.h
@@ -72,6 +72,9 @@ class PlatformSensor : public base::RefCountedThreadSafe<PlatformSensor> {
  private:
   friend class base::RefCountedThreadSafe<PlatformSensor>;
 
+  // For testing purposes.
+  friend class FakePlatformSensor;

[timvolodine, 2016/09/21 13:07:48]

if it's only to return the config map, maybe just add a config_map getter to
protected section (with the same comment "for testing purposes")?

[maksims (do not use this acc), 2016/09/26 07:09:15]

Done.

+
   mojom::SensorType type_;
   base::ObserverList<Client, true> clients_;
   ConfigMap config_map_;