Fix dangerous unsafe_get() in SensorRecord

Change raw pointers to wp<> and constify relevant lines in
SensorRecord.

Bug: 30261110

Change-Id: I7f28c593366af44192991061fa5f71cf925b22a8
(cherry picked from commit ded526e8c3539b5986b46dffc1ff8ab15d7da570)
diff --git a/services/sensorservice/SensorService.h b/services/sensorservice/SensorService.h
index 1e1ea5a..4a63ef0 100644
--- a/services/sensorservice/SensorService.h
+++ b/services/sensorservice/SensorService.h
@@ -237,7 +237,7 @@
     SortedVector< wp<SensorEventConnection> > mActiveConnections;
     bool mWakeLockAcquired;
     sensors_event_t *mSensorEventBuffer, *mSensorEventScratch;
-    SensorEventConnection const **mMapFlushEventsToConnections;
+    wp<const SensorEventConnection> * mMapFlushEventsToConnections;
     std::unordered_map<int, RecentEventLogger*> mRecentEvent;
     Mode mCurrentOperatingMode;