Don't pass x, y to test_driver_internal.click

This is because the semantics are supposed to be defined by WebDriver,
and that doesn't allow setting the x,y coordinates for the click
command (you have to use Actions for that instead). Therefore
implementations are expected to compute the coordinates rather than
use passed-in values.

By the same argument we could remove the scrollIntoView and initial
check, since those just replicate checks WebDriver already does. Since
that comes with the possibility of timing changes it isn't included in
this change.

resources/testdriver.js

@@ -211,11 +211,7 @@
                 return Promise.reject(new Error("element click intercepted error"));
             }
 
-            var rect = element.getClientRects()[0];
-            var centerPoint = getInViewCenterPoint(rect);
-            return window.test_driver_internal.click(element,
-                                                     {x: centerPoint[0],
-                                                      y: centerPoint[1]});
+            return window.test_driver_internal.click(element);
         },
 
         /**