fix crashing test due to format mismatch.

Change-Id: Ie8a60d95a19c566b1131d27f84969c0a0142c601
diff --git a/prod-tests/src/com/android/performance/tests/StartupMetricsTest.java b/prod-tests/src/com/android/performance/tests/StartupMetricsTest.java
index 52f7d50..634cee4 100644
--- a/prod-tests/src/com/android/performance/tests/StartupMetricsTest.java
+++ b/prod-tests/src/com/android/performance/tests/StartupMetricsTest.java
@@ -79,7 +79,7 @@
 
         double offlineDuration = onlineTime - startTime;
         double unavailDuration = availableTime - startTime;
-        CLog.d("Reboot: %d millis until online, %d until available",
+        CLog.d("Reboot: %f millis until online, %f until available",
                 offlineDuration, unavailDuration);
         runMetrics.put("online", Double.toString(offlineDuration/1000.0));
         runMetrics.put("bootcomplete", Double.toString(unavailDuration/1000.0));