Position: Simplify fraction support test

Also makes the test lazy to avoid any potential layouts/recalculations during
initialization.

Fixes #9898
Ref #9899

ui/position.js

@@ -41,6 +41,26 @@ var cachedScrollbarWidth, supportsOffsetFractions,
 	rpercent = /%$/,
 	_position = $.fn.position;
 
+// Support: IE <=9 only
+supportsOffsetFractions = function() {
+	var element = $( "<div>" )
+			.css( "position", "absolute" )
+			.appendTo( "body" )
+			.offset( {
+				top: 1.5,
+				left: 1.5
+			} ),
+		support = element.offset().top === 1.5;
+
+	element.remove();
+
+	supportsOffsetFractions = function() {
+		return support;
+	};
+
+	return support;
+};
+
 function getOffsets( offsets, width, height ) {
 	return [
 		parseFloat( offsets[ 0 ] ) * ( rpercent.test( offsets[ 0 ] ) ? width / 100 : 1 ),
@@ -243,7 +263,7 @@ $.fn.position = function( options ) {
 		position.top += myOffset[ 1 ];
 
 		// if the browser doesn't support fractions, then round for consistent results
-		if ( !supportsOffsetFractions ) {
+		if ( !supportsOffsetFractions() ) {
 			position.left = round( position.left );
 			position.top = round( position.top );
 		}
@@ -475,45 +495,6 @@ $.ui.position = {
 	}
 };
 
-// fraction support test
-( function() {
-	var testElement, testElementParent, testElementStyle, offsetLeft, i,
-		body = document.getElementsByTagName( "body" )[ 0 ],
-		div = document.createElement( "div" );
-
-	//Create a "fake body" for testing based on method used in jQuery.support
-	testElement = document.createElement( body ? "div" : "body" );
-	testElementStyle = {
-		visibility: "hidden",
-		width: 0,
-		height: 0,
-		border: 0,
-		margin: 0,
-		background: "none"
-	};
-	if ( body ) {
-		$.extend( testElementStyle, {
-			position: "absolute",
-			left: "-1000px",
-			top: "-1000px"
-		} );
-	}
-	for ( i in testElementStyle ) {
-		testElement.style[ i ] = testElementStyle[ i ];
-	}
-	testElement.appendChild( div );
-	testElementParent = body || document.documentElement;
-	testElementParent.insertBefore( testElement, testElementParent.firstChild );
-
-	div.style.cssText = "position: absolute; left: 10.7432222px;";
-
-	offsetLeft = $( div ).offset().left;
-	supportsOffsetFractions = offsetLeft > 10 && offsetLeft < 11;
-
-	testElement.innerHTML = "";
-	testElementParent.removeChild( testElement );
-} )();
-
 } )();
 
 return $.ui.position;