Made grid testbench tests more stable on all browsers

Made grid testbench tests more stable on all browsers

Testbench reports different things for the css width depending on
the browser so changed the tests to use the WebElement.Size property
instead to get consistant results.

Also removed the data change test as in its current state it does
not serve any purpose. A similar test could be added at some point
when we actually can test this. The test had never succeeded.

Change-Id: I8d762b1c662afb5e9b09d384b8100200fbfaba33