CSS: dimensions workaround for IE11 fullscreen quirk

Fixes jquery#1764

src/css.js

@@ -113,6 +113,13 @@ function getWidthOrHeight( elem, name, extra ) {
 		styles = getStyles( elem ),
 		isBorderBox = jQuery.css( elem, "boxSizing", false, styles ) === "border-box";
 
+	// Support: IE11+
+	// Fix for edge case in IE 11. See https://github.com/jquery/jquery/issues/1764
+	if ( !support.reliableDimensionsInFullscreenMode && window.top !== window.self &&
+		document.msFullscreenElement ) {
+		val = Math.round( elem.getBoundingClientRect()[name] * 100 );
+	}
+
 	// Some non-html elements return undefined for offsetWidth, so check for null/undefined
 	// svg - https://bugzilla.mozilla.org/show_bug.cgi?id=649285
 	// MathML - https://bugzilla.mozilla.org/show_bug.cgi?id=491668

src/css/support.js

@@ -96,7 +96,12 @@ define([
 			div.removeChild( marginDiv );
 
 			return ret;
-		}
+		},
+		// Support: IE 11
+		// IE 11 has a bug with offsetWidth / offsetHeight / getClientBoundingRect()
+		// in fullscreen mode inside an iframe the values are 100x smaller than they should be
+		// See https://connect.microsoft.com/IE/feedback/details/838286/ie-11-incorrectly-reports-dom-element-sizes-in-fullscreen-mode-when-fullscreened-element-is-within-an-iframe
+		reliableDimensionsInFullscreenMode: !( "msFullscreenElement" in document )
 	});
 })();