Make element.style["color"] work in Sky

sky/tests/layout/document-elementFromPoint.sky

 <sky>
 <style>
 foo, parent { width: 100px; height: 100px; background: blue; }
 bar { width: 100px; height: 100px; background: purple; }
 parent { display: paragraph; }
 child { background: salmon; }
 canvas { height: 50px; background-color: pink; }
 </style>
 <foo /><bar />
 <parent>
@@ skipping 29 matching lines @@
     expect(document.elementFromPoint(95, 210).tagName, equals('parent'));
     // Below the <child> inline.
     expect(document.elementFromPoint(50, 275).tagName, equals('parent'));
   }
 
   test("should hit test child and parent", () {
     hitTestWithChildren();
   });
 
   test("should hit test child with layered parent", () {
-    document.querySelector('parent').style.setProperty("transform", "translate3d(0, 0, 0)");
+    document.querySelector('parent').style["transform"] = "translate3d(0, 0, 0)";
     hitTestWithChildren();
   });
 
   test("should hit test transformed child", () {
-    document.querySelector('child').style.setProperty("transform", "translate3d(100px, 0, 0)");
+    document.querySelector('child').style["transform"] = "translate3d(100px, 0, 0)";
     expect(document.elementFromPoint(50, 210).tagName, equals('parent'));
     expect(document.elementFromPoint(150, 210).tagName, equals('child'));
   });
 
   test("should hit test canvas", () {
     expect(document.elementFromPoint(50, 310).tagName, equals('canvas'));
   });
 }
 </script>
 </sky>