Remove obsolete code from shortcut handler

These lines were introduced in 612f59aa10eef2bf6559deddfb54b84a0a30c6bc
when the only shortcuts were +/-/=/0 (to change zoom level).
Back then, when the input fields were focused, using these keys would
add these unwanted characters to the input field and change the zoom
level of the viewer. Having both operations at the same time was an
undesired event, so a check was inserted, to ignore shortcuts when
the toolbar is focused.

The #toolbar element doesn't exist any more, so these lines are obsolete.
[CRX] Pass expected length of stream to viewer

To get a progress bar for POST/FTP requests in Chromium.
Handle navigation keys when viewer is not focused

Restrict the scrollbar hack to the keycode for "spacebar",
since the bug only occurs in Firefox with spacebar.

Keyboard navigation is only activated for the spacebar if
the currently focused element is not a button.
Fix wrong page being displayed when entering/exiting Presentation mode with zoom set to 'page-fit'
Merge pull request #4224 from Rob--W/shortcut-responsiveness

Focus container when arrow/navigation keys are pressed
Merge pull request #4229 from Rob--W/crx-stream-progress

Get progress bar for PDF streams in Chromium by passing the expected content length to the page
Fix spacebar scrolling in Firefox (4224 follow-up)
Merge pull request #4341 from Snuffleupagus/issue-4224-followup

Fix spacebar scrolling in Firefox (4224 follow-up)
Merge pull request #4292 from Snuffleupagus/issue-4232

Fix wrong page being displayed when entering/exiting Presentation mode with zoom set to 'page-fit'