Pass correct client coordinates for mouse events synthesized from a GestureTap

LayoutTests/fast/events/touch/gesture/gesture-tap-scrolled-expected.txt

+Verifies that a tap occuring in a scrolled page has the correct co-ordinates
+
+On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
+
+
+Sending GestureTapDown to 50,50
+Sending GestureShowPress
+Sending GestureTap
+Received mousemove in page
+PASS event.screenX is point.x
+PASS event.screenY is point.y
+PASS event.clientX is point.x
+PASS event.clientY is point.y
+PASS event.pageX is point.x + scrollOffset.x
+PASS event.pageY is point.y + scrollOffset.y
+Received mousedown in page
+PASS event.screenX is point.x
+PASS event.screenY is point.y
+PASS event.clientX is point.x
+PASS event.clientY is point.y
+PASS event.pageX is point.x + scrollOffset.x
+PASS event.pageY is point.y + scrollOffset.y
+Received mouseup in page
+PASS event.screenX is point.x
+PASS event.screenY is point.y
+PASS event.clientX is point.x
+PASS event.clientY is point.y
+PASS event.pageX is point.x + scrollOffset.x
+PASS event.pageY is point.y + scrollOffset.y
+Received click in page
+PASS event.screenX is point.x
+PASS event.screenY is point.y
+PASS event.clientX is point.x
+PASS event.clientY is point.y
+PASS event.pageX is point.x + scrollOffset.x
+PASS event.pageY is point.y + scrollOffset.y
+PASS eventReceived.mousemove is true
+PASS eventReceived.mousedown is true
+PASS eventReceived.mouseup is true
+PASS eventReceived.click is true
+PASS successfullyParsed is true
+
+TEST COMPLETE
+