Fix bug incrementing log time

Log start time was being incremented by the latest log event (being
added) instead of the first log event (being removed).

Test: manual
Change-Id: I4e15ba775d65d766ef0030d9cdfabe1f020185e6

services/core/java/com/android/server/utils/eventlog/LocalEventLog.java

@@ -99,6 +99,7 @@ public abstract class LocalEventLog {
     private long mLastLogRealtimeMs;
 
     public LocalEventLog(int size) {
+        Preconditions.checkArgument(size > 0);
         mLog = new Log[size];
         mLogSize = 0;
         mLogEndIndex = 0;
@@ -163,7 +164,7 @@ public abstract class LocalEventLog {
 
         if (mLogSize == mLog.length) {
             // if log is full, size will remain the same, but update the start time
-            mStartRealtimeMs += event.getTimeDeltaMs();
+            mStartRealtimeMs += mLog[startIndex()].getTimeDeltaMs();
         } else {
             // otherwise add an item
             mLogSize++;