Skip persisting when there's no change.

Only request the persisted file be updated when we have actually
modified something inside the job.

Bug: 141645789
Test: N/A
Change-Id: I7764923817573d76be071aa076cd0a3a6f41d4ec

apex/jobscheduler/service/java/com/android/server/job/JobServiceContext.java

@@ -727,8 +727,11 @@ public final class JobServiceContext implements ServiceConnection {
                     // Exception-throwing-can down the road to JobParameters.completeWork >:(
                     return true;
                 }
-                mService.mJobs.touchJob(mRunningJob);
-                return mRunningJob.completeWorkLocked(workId);
+                if (mRunningJob.completeWorkLocked(workId)) {
+                    mService.mJobs.touchJob(mRunningJob);
+                    return true;
+                }
+                return false;
             }
         } finally {
             Binder.restoreCallingIdentity(ident);

apex/jobscheduler/service/java/com/android/server/job/controllers/JobStatus.java

@@ -828,6 +828,10 @@ public final class JobStatus {
         }
     }
 
+    /**
+     * Returns {@code true} if the JobWorkItem queue was updated,
+     * and {@code false} if nothing changed.
+     */
     public boolean completeWorkLocked(int workId) {
         if (executingWork != null) {
             final int N = executingWork.size();