Replaced threads by executor

app/src/main/java/eu/faircode/email/ServiceSend.java

@@ -62,8 +62,6 @@ import javax.mail.Session;
 import javax.mail.internet.InternetAddress;
 import javax.mail.internet.MimeMessage;
 
-import static android.os.Process.THREAD_PRIORITY_BACKGROUND;
-
 public class ServiceSend extends ServiceBase implements SharedPreferences.OnSharedPreferenceChangeListener {
     private TupleUnsent lastUnsent = null;
     private Network lastActive = null;
@@ -706,10 +704,12 @@ public class ServiceSend extends ServiceBase implements SharedPreferences.OnShar
     }
 
     static void boot(final Context context) {
-        Thread thread = new Thread(new Runnable() {
+        executor.submit(new Runnable() {
             @Override
             public void run() {
                 try {
+                    EntityLog.log(context, "Boot send service");
+
                     DB db = DB.getInstance(context);
 
                     EntityFolder outbox = db.folder().getOutbox();
@@ -726,9 +726,7 @@ public class ServiceSend extends ServiceBase implements SharedPreferences.OnShar
                     Log.e(ex);
                 }
             }
-        }, "send:boot");
-        thread.setPriority(THREAD_PRIORITY_BACKGROUND);
-        thread.start();
+        });
     }
 
     static void start(Context context) {

app/src/main/java/eu/faircode/email/ServiceSynchronize.java

@@ -111,6 +111,8 @@ public class ServiceSynchronize extends ServiceBase implements SharedPreferences
     private MutableLiveData<List<TupleAccountState>> liveAccountState = new MutableLiveData<>();
     private MediatorState liveAccountNetworkState = new MediatorState();
 
+    private static ExecutorService executor = Helper.getBackgroundExecutor(1, "sync");
+
     private static final long PURGE_DELAY = 30 * 1000L; // milliseconds
     private static final long QUIT_DELAY = 5 * 1000L; // milliseconds
     private static final long STILL_THERE_THRESHOLD = 3 * 60 * 1000L; // milliseconds
@@ -2138,10 +2140,12 @@ public class ServiceSynchronize extends ServiceBase implements SharedPreferences
     }
 
     static void boot(final Context context) {
-        Thread thread = new Thread(new Runnable() {
+        executor.submit(new Runnable() {
             @Override
             public void run() {
                 try {
+                    EntityLog.log(context, "Boot sync service");
+
                     DB db = DB.getInstance(context);
                     try {
                         db.beginTransaction();
@@ -2187,9 +2191,7 @@ public class ServiceSynchronize extends ServiceBase implements SharedPreferences
                     Log.e(ex);
                 }
             }
-        }, "synchronize:boot");
-        thread.setPriority(THREAD_PRIORITY_BACKGROUND);
-        thread.start();
+        });
     }
 
     private static void schedule(Context context, boolean sync) {