Vibration API: use the [Clamp] attribute.

This makes it so that Javascript input of -1 is converted
to 0 rather than 4294967295.

BUG=310138

Review URL: https://codereview.chromium.org/30693008

git-svn-id: svn://svn.chromium.org/blink/trunk@160235 bbb929c8-8fbe-4397-9dbb-9b2b20218538