Don't force layout for mouse event hit tests

LayoutTests/fast/events/script-tests/page-scaled-mouse-click.js

Index: LayoutTests/fast/events/script-tests/page-scaled-mouse-click.js
diff --git a/LayoutTests/fast/events/script-tests/page-scaled-mouse-click.js b/LayoutTests/fast/events/script-tests/page-scaled-mouse-click.js
index 0d80b73b8e45694921874ad632d507e719c1125c..06a7964318966d84ce8931a370ada93f60d48e4f 100644
--- a/LayoutTests/fast/events/script-tests/page-scaled-mouse-click.js
+++ b/LayoutTests/fast/events/script-tests/page-scaled-mouse-click.js
@@ -44,6 +44,9 @@ function testEvents(button, description, expectedString) {
 }
 
 if (window.eventSender && window.internals) {
+    // Mouse events only work after an initial layout
+    document.body.offsetLeft;
+
     eventSender.mouseMoveTo(10, 10);
     // We are clicking in the same position on screen. As we scale or transform the page,
     // we expect the pageX and pageY event coordinates to change because different