Select: drop down sizing problems

[bill]

There are two sizing problems with the Select drop down menu, which become a bit more apparent with the new claro theme but were actually present before.

1. no hover effect on right edge of MenuItem

Notice how the right edge of the menu item doesn't have the blue hover effect:

2. horizontal scroll bar appears

In both cases the problem deals with sizing of the inner <table> node to match the size of the wrapper <div> node, where the wrapper <div> node's content-size will vary depending on the presence of a vertical scrollbar and the width of the scrollbar, which depends on the browser and OS.

[bill]

hover effect problem

[bill]

horizontal scrollbar problem

[bill]

(In [21669]) Various fixes/simplifications so that Select's dropdown's inner <table> node is neither too wide nor too narrow. Main fix is to use width: 100% on <table> rather than having browser specific code to gauge width of scroll bar.

I think this brings _HasDropDown in line with how ComboBox is dealing with it's drop down.

Fixes #10923 !strict.

[bill]

(In [22248]) Fix regression from [21669], case problem causing unwanted horizontal scrollbar on webkit. Refs #10923, fixes #11205 !strict.