Fix document loading with zoom set to 'page-fit', regression from #2719

[Snuffleupagus]

This PR fixes an issue when the PDF document is loaded with zoom set to 'page-fit'.
Currently, once the progressive loading bar is removed, the pages will be slightly shorter than the viewer height. To see this issue, try opening: http://mozilla.github.io/pdf.js/web/viewer.html#page=2&zoom=page-fit.

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Published

• Viewer: http://107.21.233.14:8877/f735df845f2e94c/web/viewer.html
• Extension: http://107.21.233.14:8877/f735df845f2e94c/extensions/firefox/pdf.js.xpi
• Extension (AMO): http://107.21.233.14:8877/f735df845f2e94c/extensions/firefox/pdf.js.amo.xpi

[yurydelendik]

I think it will be much better if we will not change the view height because of the progress bar. Can we overlay the bar on top of the pages?

[Snuffleupagus]

I think it will be much better if we will not change the view height because of the progress bar. Can we overlay the bar on top of the pages?

I think that would re-introduce the visual bug described here: #2719 (comment).

I suppose that we could instead just ignore the height of the progressive loading bar, here: https://github.com/Snuffleupagus/pdf.js/blob/f6e1c9e23122c7c8054003355a11d8bdcda7f24c/web/viewer.js#L800.
The only issue with that solution is that it wouldn't look as good, since the pages wouldn't fit perfectly in the viewer until the loading bar was removed.

@yurydelendik Visually I prefer my solution, but from a performance perspective your solution is a lot better since it avoids having to rescale the document. Should I implement your idea instead?

[yurydelendik]

I'm afraid we have too much specialized / branched logic for UI already without it's being tested. So it's good as simple solution as possible. (Even if it will introduce the visual bug above)

Let's try "window resize" logic here. See https://github.com/mozilla/pdf.js/blob/master/web/viewer.js#L3170, we can add it near https://github.com/mozilla/pdf.js/blob/master/web/viewer.js#L1377. That might be easier to follow, I think

[Snuffleupagus]

Closing in favour of #3332.