Fixing calc() parameter parsing in cubic-bezier functions

Before this patch, calc values in cubic-bezier functions
weren't being read correctly since they were handled as
simple floats.

R=rob.buis@samsung.com,timloh@chromium.org,alancutter@chromium.org
BUG=388332

Review URL: https://codereview.chromium.org/369313002

git-svn-id: svn://svn.chromium.org/blink/trunk@178998 bbb929c8-8fbe-4397-9dbb-9b2b20218538