Add more log to track down the "idle until changed" issue.

Bug 34724174
Test: Tested manually with intentionally adding a bug.

Change-Id: I1789285068203b22ce271180667eb9cb1eb0b182

services/core/java/com/android/server/AlarmManagerService.java

@@ -1239,6 +1239,11 @@ class AlarmManagerService extends SystemService {
                     mAllowWhileIdleDispatches.add(ent);
                 }
             }
+            if ((mPendingIdleUntil != a) && (mPendingIdleUntil != null)) {
+                Slog.wtfStack(TAG, "setImplLocked: idle until changed from " + mPendingIdleUntil
+                        + " to " + a);
+            }
+
             mPendingIdleUntil = a;
             mConstants.updateAllowWhileIdleMinTimeLocked();
             needRebatch = true;