Remove deprecated setInitializeAtMinimumPageScale() function from WebSettings.

This function was removed from Chromium so we can safely remove it now.

BUG=None
TEST=None
R=abarth@chromium.org

Review URL: https://codereview.chromium.org/57563009

git-svn-id: svn://svn.chromium.org/blink/trunk@161337 bbb929c8-8fbe-4397-9dbb-9b2b20218538