Remove useless AdjustViewSizeOrNot enum

Only one of the two possible values was ever used.

R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/165193003

git-svn-id: svn://svn.chromium.org/blink/trunk@167136 bbb929c8-8fbe-4397-9dbb-9b2b20218538