Add GalleryProvider.cancelRequest(int), fix SpiderQueen.request(int, boolean)

app/src/main/java/com/hippo/ehviewer/download/DownloadService.java

@@ -41,6 +41,7 @@ import com.hippo.yorozuya.SimpleHandler;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 
+// TODO Stop and delete action should not pass through DownloadService
 public class DownloadService extends Service implements DownloadManager.DownloadListener {
 
     public static final String ACTION_START = "start";