Admin bar sub-menu shadows bleed "up" into parent container

[jakemgold]

It's subtle, and seems to vary in intensity between both browsers and Windows / OS X, probably due to different hardware acceleration / anti-aliasing handling.

On Windows, I can only see it on Firefox (tested with 7); IE9 and Chrome appear fine. A colleague can see it in Chrome and Firefox on OS X. Probably anti-aliasing differences between the OS's / browsers.

Reducing shadow strength to 3px seems to fix it for me, but not sure if the aesthetic change is desirable. It's more complex, but we could also give the parent container's anchor a white background and z-index it above the submenu UL.

Subtle shadow bleeding up into parent

Used z-index / background color solution for a more definitive solution

Seems to cause an issue with the W menu when mouse is over the submenu: ​http://cl.ly/0J432c2H3C0h3o152r1f

Forthcoming revised patch only applies new style to anchor, not inner span, address the W issue Helen caught.

modifies last patch to fix W issue

I'll review the patch and guide the fix into core.

In [19403]:

Tighten admin bar submenu shadows. fixes #19186.