Don't turn middleclicks into click events.

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

Index: LayoutTests/fast/events/script-tests/mouse-click-events.js
diff --git a/LayoutTests/fast/events/script-tests/mouse-click-events.js b/LayoutTests/fast/events/script-tests/mouse-click-events.js
index 13b6e62d914ed74b09815a5d8adc8ce7e647f414..a2e311329a406fe3943462927bcb72b58e946fd7 100644
--- a/LayoutTests/fast/events/script-tests/mouse-click-events.js
+++ b/LayoutTests/fast/events/script-tests/mouse-click-events.js
@@ -29,6 +29,10 @@ if (window.eventSender)
     eventSender.mouseMoveTo(10, 10);
 
 function sendEvents(button) {
+    if (button < 0 || button > 2) {
+        testFailed("eventSender only supports button 0 (left), 1 (middle) and 2 (right).");
+        return;
+    }
     if (!window.eventSender) {
         debug("This test requires DumpRenderTree.  Click on the blue rect with different mouse buttons to log.")
         return;
@@ -51,5 +55,4 @@ if (window.eventSender) {
     testEvents("Left Mouse Button", 0, "mousedown(0) mouseup(0) click(0) mousedown(0) mouseup(0) click(0) dblclick(0) ");
     testEvents("Middle Mouse Button", 1, "mousedown(1) mouseup(1) click(1) mousedown(1) mouseup(1) click(1) dblclick(1) ");
     testEvents("Right Mouse Button", 2, "mousedown(2) mouseup(2) mousedown(2) mouseup(2) ");
-    testEvents("4th Mouse Button", 3, "mousedown(1) mouseup(1) click(1) mousedown(1) mouseup(1) click(1) dblclick(1) ");
 }