BUG: 213508 Shifts focus to the document when collapsing a sidebar view

*Summary:

If we click on a sidebar item to collapse it, the focus remains on the sidebar item list and pressing the up/down arrow, j, k or page up/down key doesn't scroll the document, instead iterates through the sidebar items. Applying this patch, the focus shifts to the document on collapsing the sidebar. If the sidebar is collapsed when the document is not opened, the focus shifts away from it.

BUG: 213508

*Test Plan

Open a PDF document
The sidebar becomes active showing contents or thumbnails
The user doesn't want to see them, so clicks on the sidebar active item to hide the contents/thumbnails pane
To scroll the page, the user presses the up/down arrow, j, k or page up/down key
The sidebar items iterates instead of scrolling of document
Applying this patch, the document should be scrolled in step 4