Update DownloadRunnable.java

add description

app/src/main/java/us/shandian/giga/get/DownloadRunnable.java

@@ -117,6 +117,8 @@ public class DownloadRunnable extends Thread {
                     byte[] buf = new byte[DownloadMission.BUFFER_SIZE];
                     int len;
 
+                    // use alwways start <= end
+                    // fixes a deadlock in DownloadRunnable because youtube is sending one byte alone after downloading 26MiB exactly
                     while (start <= end && mMission.running && (len = is.read(buf, 0, buf.length)) != -1) {
                         f.write(buf, 0, len);
                         start += len;