Handle lack of .width and .height from getBoundingClientRect() in IE8

Closes #14093
Correction to #14090
Relevant docs: https://developer.mozilla.org/en-US/docs/Web/API/Element.getBoundingClientRect#Browser_compatibility
Merge pull request #14492 from twbs/ie8-getBoundingClientRect

Handle lack of .width and .height from getBoundingClientRect() in IE8
G R U N T