improve sensorservice dumpsys

Change-Id: I8b53d5cab884c3aca16d95df5fbf288368d52e8b
diff --git a/services/sensorservice/SensorDevice.h b/services/sensorservice/SensorDevice.h
index c19b2ce..728b6cb 100644
--- a/services/sensorservice/SensorDevice.h
+++ b/services/sensorservice/SensorDevice.h
@@ -37,11 +37,14 @@
     friend class Singleton<SensorDevice>;
     struct sensors_poll_device_t* mSensorDevice;
     struct sensors_module_t* mSensorModule;
-    Mutex mLock; // protect mActivationCount[].rates
+    mutable Mutex mLock; // protect mActivationCount[].rates
     // fixed-size array after construction
     struct Info {
-        Info() { }
+        Info() : delay(0) { }
         KeyedVector<void*, nsecs_t> rates;
+        nsecs_t delay;
+        status_t setDelayForIdent(void* ident, int64_t ns);
+        nsecs_t selectDelay();
     };
     DefaultKeyedVector<int, Info> mActivationCount;