Memory issue when streaming a PDF

[automatedbugreportingfacility]

This is a regression. Loading the following pdf causes the browser to consume large amounts of memory (>2 GB here) until it hits OOM. Please note that:

1. It won't reproduce locally, it must be loaded from the URL.
2. The pdf file must not be in cache, ie. clear it (Ctrl + Shift + Delete) if the problem stops reproducing.

URL: http://www.gergs-blum.de/Mensa%20KCG/Bauen%20mit%20Holz%205%202014.pdf

c3f191a is the first bad commit
commit c3f191a
Author: Yury Delendik
Date: Fri Sep 5 20:02:54 2014 -0500

Implement streaming using moz-chunk-arraybuffer

[automatedbugreportingfacility]

By the way, this is not a dupe of #5329, at least the patches from PR #5332 don't seem to resolve this issue.

[Snuffleupagus]

Loading the following pdf causes the browser to consume large amounts of memory (>2 GB here) until it hits OOM.

With streaming enabled, I can reproduce the large memory consumption (over 2 GB), and very intermittently I'm also getting OOM errors.
However, with streaming disabled, the memory consumption is a lot lower (about 500 MB), so streaming apparently requires a lot more memory.

/cc @yurydelendik Is there anything (simple) we can do to reduce the memory consumption of streaming?

[Snuffleupagus]

The reason for the difference between streaming/non-streaming is probably related to the differences between getData (PdfStreamConverter.jsm#L209) and readData (PdfStreamConverter.jsm#L204).
In the first case we delete this.data, which we cannot do in latter case, and this should explain why the memory consumption is so different.

[automatedbugreportingfacility]

Right, adding "delete this.data;" before "return data;" fixes the issue for me.

[Snuffleupagus]

Right, adding "delete this.data;" before "return data;" fixes the issue for me.

As I alluded to above, we cannot do that since it breaks streaming (it would be functionally equivalent to disableStream=true), so this is unfortunately not a solution.