Remove the precision="float" attribute on <input type="range">

Intent to Deprecate and Remove:
https://groups.google.com/a/chromium.org/d/msg/blink-dev/-OvFrybkW1E/Ucrct3sm6foJ

Review URL: https://codereview.chromium.org/301563002

git-svn-id: svn://svn.chromium.org/blink/trunk@174965 bbb929c8-8fbe-4397-9dbb-9b2b20218538