BorderContainer: focus on splitters is not visible in Firefox

[Becky Gibson]

This was found in 1.2b1 as well as 09/02/08 nightly. Resizable splitters are in the tab order and get focus so the user can adjust the size of a pane via the arrow keys (although resizing is currently broken #7582). In Firefox 3 focus on the splitters is barely noticeable - it can only be seen on the very edges of the splitter. In high contrast mode focus can not be seen at all. This worked properly in 1.1 in Firefox 2 & 3 as well as IE (see ​http://download.dojotoolkit.org/release-1.1.1/dojo-release-1.1.1/dijit/tests/layout/test_BorderContainer.html). The problem currently only exists in Firefox 2&3, IE 7 is still fine.

Focus on the splitters needs to be visible in standard as well as Windows high contrast mode.

[nonken]

(In [15206]) Changed z-index of splitter to bring back border on focus, fixes #7583

[bill]

Hmm, this presumably negates the effects of [14392] and causes #6438 to occur.

[bill]

(In [16064]) Give splitters a high z-index on FF, low on IE, so that FF correctly shows splitter focus, but that on IE the splitters don't cover up the borders of panes.

Also fixes problem seen in themeTester.html (non-active sizing) where the splitter being dragged appears behind the stationary splitters.

ISTM that FF/high-contrast focus on splitters is still very difficult to see though, both before and after this change.

Refs #6438, #7583.

[bill]

Reopening this ticket since focus on firefox in high-contrast mode is still near impossible to see. Only the "short" ends of the splitter have the dotted border.

[bill]

Patch looks good to me, surely it won't break anything.

[bill]

From Becky's check in:

(In [22359]) fixes #7583 create a class to make high contrast focus on border container splitters visible in FF