Add support for the column-fill property.

LayoutTests/fast/multicol/hit-test-float.html

 <style>
     #target { width: 50px; height: 50px; background-color: red; margin: 10px; }
     #target:hover { background-color: green; }
 </style>
 <p>
     Test for <i><a href="https://bugs.webkit.org/show_bug.cgi?id=44730">https://bugs.webkit.org/show_bug.cgi?id=44730</a>
     Floats inside of multicol fail to hit test</i>.
 </p>
 <p>
     The red square should turn green when hovered.
 </p>
-<div style="margin: 100; width: 300; height: 200; outline: solid black; -webkit-columns: 2;">
+<div style="-webkit-columns:2; columns:2; column-fill:auto; margin: 100; width: 300; height: 200; outline: solid black;">
     <div>
         <div style="height: 250px; background-color: purple;"></div>
         <div style="float: right; background-color: lightyellow; margin: 5px;">
             <div id="target"></div>
         </div>
     </div>
 </div>
 <div id="result">FAIL: Test did not run.</div>
 <script>
     if (window.testRunner)
         testRunner.dumpAsText();
 
     var result = document.getElementById("result");
     var hitElement = document.elementFromPoint(370, 250);
     if (hitElement === document.getElementById("target"))
         result.innerText = "PASS";
     else
         result.innerText = "FAIL: Hit " + hitElement;
 </script>