Remove WebTestDelegate::setClientWindowRect.

This method has no users. It should go away.

R=jochen,dcarney,jamesr
BUG=

Review URL: https://codereview.chromium.org/49003006

git-svn-id: svn://svn.chromium.org/blink/trunk@160753 bbb929c8-8fbe-4397-9dbb-9b2b20218538