Disable deferred image decoding for GIFs due to performance regression

Temporarily the feature of defer decoding multi-frame images.

TBR=senorblanco@chromium.org
BUG=260052

Review URL: https://chromiumcodereview.appspot.com/19634006

git-svn-id: svn://svn.chromium.org/blink/trunk@154726 bbb929c8-8fbe-4397-9dbb-9b2b20218538