Remove GraphicsContext::applyDeviceScaleFactor()

Unnecessary GC::scale() alias.

R=schenney@chromium.org,senorblanco@chromium.org
BUG=424655

Review URL: https://codereview.chromium.org/725043002

git-svn-id: svn://svn.chromium.org/blink/trunk@185388 bbb929c8-8fbe-4397-9dbb-9b2b20218538