Don't force layout for mouse event hit tests

LayoutTests/scrollbars/scrollbar-miss-mousemove-disabled.html

Index: LayoutTests/scrollbars/scrollbar-miss-mousemove-disabled.html
diff --git a/LayoutTests/scrollbars/scrollbar-miss-mousemove-disabled.html b/LayoutTests/scrollbars/scrollbar-miss-mousemove-disabled.html
index 8c79e4655d7e4926c892c9e19db9550cb04b607e..91cc45574e485ee88894d2ab9a6ce29b45420f1c 100644
--- a/LayoutTests/scrollbars/scrollbar-miss-mousemove-disabled.html
+++ b/LayoutTests/scrollbars/scrollbar-miss-mousemove-disabled.html
@@ -117,6 +117,9 @@ disabled control case. On success, the text should begin with "zx".<p/>
 <div id="console"></div>
 <script>
 if (window.eventSender) {
+    // Mouse events only work after an initial layout
+    document.body.offsetLeft;
+
     document.form1.text1.disabled = true;
     document.form1.style.display = "none";
     eventSender.mouseMoveTo(390, 10);