ETA calculation is broken when setting some files to 'Do Not Download'

[peterhoeg]

Problem: When calculating ETA the total downloaded size is not only taking the downloaded size of the selected file into consideration but also downloaded size of files set to 'Do Not Download'.

How to reproduce (sizes mentioned are just examples):

a) Start downloading a torrent with two files in it each with a size of 100MB. Total size to download it then 200MB.

b) Wait for more than 100MB of download (example: both files are downloaded 51% - 51MB each, total of 102MB).

c) Set one of the files to 'Do Not Download'

d) Deluge now thinks that since is has already downloaded more than the required 100MB that it is finished and thus stops calculating ETA.

Expected behaviour:

Deluge should only consider what is downloaded on the files not set to 'Do Not Download'.