Default flush implementation for Sensors 2.0

Bug: 111070257
Test: Builds, passes corresponding VTS tests
Change-Id: I5b46232ffb0dd2c85bccd9dad34dd04d29a5677d
diff --git a/sensors/2.0/default/Sensor.h b/sensors/2.0/default/Sensor.h
index e467b56..75d9aab 100644
--- a/sensors/2.0/default/Sensor.h
+++ b/sensors/2.0/default/Sensor.h
@@ -25,6 +25,7 @@
 #include <vector>
 
 using ::android::hardware::sensors::V1_0::Event;
+using ::android::hardware::sensors::V1_0::Result;
 using ::android::hardware::sensors::V1_0::SensorInfo;
 using ::android::hardware::sensors::V1_0::SensorType;
 
@@ -48,6 +49,7 @@
     const SensorInfo& getSensorInfo() const;
     void batch(int32_t samplingPeriodNs);
     void activate(bool enable);
+    Result flush();
 
    protected:
     void run();