Remove old attributes from AudioParam

The following attributes of AudioParam are no longer part of the
WebAudio spec and should be removed: minValue, maxValue, name, units.

See http://webaudio.github.io/web-audio-api/#idl-def-AudioParam

Update delaynode test since it checked the values of minValue and
maxValue.

BUG=396910
TESTS=No change in behavior except for incorrect delaynode test.

Review URL: https://codereview.chromium.org/417853002

git-svn-id: svn://svn.chromium.org/blink/trunk@179272 bbb929c8-8fbe-4397-9dbb-9b2b20218538