Don't do HiDPI scaling of accelerated filter params in Blink.

This puts HiDPI scaling of filter parameters behind a
compile-time flag (that is already enabled in Chrome). CC
will take care of DPR on the accelerated side in an upcoming
change, and FilterEffectRenderer will take care of it on the
raster side.

BUG=281516
R=jamesr@chromium.org

Review URL: https://codereview.chromium.org/191053003

git-svn-id: svn://svn.chromium.org/blink/trunk@168788 bbb929c8-8fbe-4397-9dbb-9b2b20218538