After the refactoring in PR 5678, the B2G viewer now prints the following in the console:
```
ReferenceError: DownloadManager is not defined
```
This will obviously not matter once the B2G viewer is replaced with the new components-based one. But until that happens, I think it makes sense to just stub the class to suppress the error.
For consistency, this preference should be placed amongst the others. The current position is purely for "historical" reasons, since it was one of the first preferences that was added to the code.
In Blink-based browsers, there is a mismatch between document size and
paper size. Even if exactly the same values and unit are used, it is
possible that the printed results takes more pages than expected.
To solve the issue, the page size is set via @page size, and the canvas
and ancestor nodes are assigned a width+height of 100% (=relative to the
page). This change resolves bugs such as blank pages and split pages.
This patch also rearrange the order of the references to the DOM elements of the predefined zoom values, in viewer.js, to correspond with the element order in the current viewer UI. (The previous ordering is a leftover from the previous viewer UI.)
Instead of trying to hack around various browser defects, let's just disable PresentationMode in the affected browsers. This patch:
- Disables PresentationMode in IE11+ when the viewer is embedded; fixes 4711.
From reading IRC scrollback, it became clear that having to manually call `PDFFindController.resolveFirstPage` in order for the find functionality to work isn't particulary good. Hence this PR, which moves that code into `PDFViewer.setDocument` to make life easier for third-party implementations.
We can pass it in using the options object. Note that that this also avoids creating a DownloadManager object for each separate link (instead, having only one is enough).
Currently if you manage to e.g. open the console (with <kbd>Ctrl</kbd>+<kbd>Shift</kbd>+<kbd>K</kbd>) before the viewer is initialized, the following will be printed in the console: `TypeError: pdfViewer is null`.
This doesn't cause any actual errors, but nevertheless it seems like something we should avoid.
Followup to PR 5413.
Since `preferenceSidebarViewOnLoad` is an enumeration value, it seems better to initialize it with the default one instead of a boolean.
`preferencesPdfBugEnabled` uses a superfluous "s", which is a typo I made when I introduced it.
