Core: Only use mousedown to prevent text selection in browsers that don't support selectstart. Fixes #6080 - Core: disableSelection() disables select elements in Chrome.
Core: Only use mousedown to prevent text selection in browsers that don't support selectstart. Fixes #6080 - Core: disableSelection() disables select elements in Chrome.

GrayYoung/jQuery.UI.Extension,GrayYoung/jQuery.UI.Extension