Don't force layout for mouse event hit tests

LayoutTests/editing/selection/script-tests/click-outside-editable-div.js

 description("Ensure that clicking in the margins around editable divs does not grant focus.")
 
 document.body.style.margin = "20px";
 
 var outerDiv = document.createElement("div");
 outerDiv.style.cssText = "width: 100px; padding: 100px; background-color: blue;";
 var innerDiv = document.createElement("div");
 innerDiv.style.cssText = "height: 100px; border: 1px solid pink; background-color: green;";
 innerDiv.contentEditable = true;
 outerDiv.appendChild(innerDiv);
 document.body.insertBefore(outerDiv, document.body.firstChild);
 
+// Mouse events only work after an initial layout
+document.body.offsetLeft;
+
 var lastClickCausedFocus = false;
 document.documentElement.addEventListener("mouseup", function(e) {
     var lastClick = e || window.event;
     if (lastClickCausedFocus) {
         testFailed("Click @ " + lastClick.clientX + ", " + lastClick.clientY + " caused innerdiv to focus!");
     } else {
         testPassed("Click @ " + lastClick.clientX + ", " + lastClick.clientY + " did not cause focus.");
     }
     innerDiv.blur();
     lastClickCausedFocus = false;
@@ skipping 17 matching lines @@
 
     clickAt(70, 270);
     clickAt(170, 270);
     clickAt(270, 270);
 } else {
     debug("To test, cick above and to the left of the blue box, then above it, then to the left " +
           "of it and finally, click in all 8 regions around the green div.");
 }
 
 var successfullyParsed = true;