Merge "Fixes a thread safety issue (a time-of-check-time-of-use bug) in BatteryExternalStatsWorker that causes system_server crashes in VROS device."

services/core/java/com/android/server/am/BatteryExternalStatsWorker.java

@@ -399,7 +399,7 @@ class BatteryExternalStatsWorker implements BatteryStatsImpl.ExternalStatsSync {
         }
     }
 
-    public void shutdown() {
+    public synchronized void shutdown() {
         mExecutorService.shutdownNow();
     }