healthd: init members of BatteryMonitor.

Bug: 26879394
Change-Id: I09a6c78137f91a0c88bf4ba1e8890b4ec31dcf2c
diff --git a/healthd/BatteryMonitor.h b/healthd/BatteryMonitor.h
index a61171f..6001073 100644
--- a/healthd/BatteryMonitor.h
+++ b/healthd/BatteryMonitor.h
@@ -37,6 +37,7 @@
         ANDROID_POWER_SUPPLY_TYPE_BATTERY
     };
 
+    BatteryMonitor();
     void init(struct healthd_config *hc);
     bool update(void);
     status_t getProperty(int id, struct BatteryProperty *val);