Blink gardening: fast/encoding/api/streaming-decode.html crash flakily

TBR=enne@chromium.org
NOTRY=true
BUG=305476

Review URL: https://codereview.chromium.org/26656002

git-svn-id: svn://svn.chromium.org/blink/trunk@159202 bbb929c8-8fbe-4397-9dbb-9b2b20218538