Don't force layout for mouse event hit tests

LayoutTests/svg/custom/pointer-events-with-linecaps-and-miterlimits.xhtml

Index: LayoutTests/svg/custom/pointer-events-with-linecaps-and-miterlimits.xhtml
diff --git a/LayoutTests/svg/custom/pointer-events-with-linecaps-and-miterlimits.xhtml b/LayoutTests/svg/custom/pointer-events-with-linecaps-and-miterlimits.xhtml
index d1cb38fb8ca53e90b641095a04869d5a3f96fc9a..3612affb390367de2784126a1b519daeacf3e7b9 100644
--- a/LayoutTests/svg/custom/pointer-events-with-linecaps-and-miterlimits.xhtml
+++ b/LayoutTests/svg/custom/pointer-events-with-linecaps-and-miterlimits.xhtml
@@ -56,6 +56,8 @@ if (window.testRunner) {
 }
 
 if (window.eventSender) {
+    // Mouse events only work after an initial layout
+    document.body.offsetLeft;
     eventSender.mouseMoveTo(1, 1);
     eventSender.mouseDown();
 }