Fix puller for SystemUptime

The SystemUptime atom puller was incorrectly calling SystemClock's
elapsedRealtime function instead of uptimeMillis.

Test: make
Test: adb cmd stats pull-source 10015
Bug: 150803469
Change-Id: Iab3ddf127f8c27c10b41bc4931222567b75417e5
diff --git a/services/core/java/com/android/server/stats/pull/StatsPullAtomService.java b/services/core/java/com/android/server/stats/pull/StatsPullAtomService.java
index fd275d8..f1f5bfe 100644
--- a/services/core/java/com/android/server/stats/pull/StatsPullAtomService.java
+++ b/services/core/java/com/android/server/stats/pull/StatsPullAtomService.java
@@ -1292,7 +1292,7 @@
     int pullSystemUptime(int atomTag, List<StatsEvent> pulledData) {
         StatsEvent e = StatsEvent.newBuilder()
                 .setAtomId(atomTag)
-                .writeLong(SystemClock.elapsedRealtime())
+                .writeLong(SystemClock.uptimeMillis())
                 .build();
         pulledData.add(e);
         return StatsManager.PULL_SUCCESS;