Don't force layout for mouse event hit tests

LayoutTests/fast/images/script-tests/imagemap-dynamic-area-updates.js

Index: LayoutTests/fast/images/script-tests/imagemap-dynamic-area-updates.js
diff --git a/LayoutTests/fast/images/script-tests/imagemap-dynamic-area-updates.js b/LayoutTests/fast/images/script-tests/imagemap-dynamic-area-updates.js
index cba734fb013e626957c5a840440149f5ee6d09e2..6f829336c7a00febe5adbb525bd334ac07f86ed3 100644
--- a/LayoutTests/fast/images/script-tests/imagemap-dynamic-area-updates.js
+++ b/LayoutTests/fast/images/script-tests/imagemap-dynamic-area-updates.js
@@ -25,6 +25,9 @@ map.appendChild(area);
 document.body.appendChild(image);
 document.body.appendChild(map);
 
+// Mouse events only work after an initial layout
+document.body.offsetLeft;
+
 function setArea(shape, coords)
 {
     area.setAttribute('shape', shape);