Remove redundant scheduleDelayedAction in Audio constructor

Setting the src attribute will trigger HTMLMediaElement::parseAttribute,
which already calls scheduleDelayedAction when src is modified.

This is already tested by LayoutTests/media/audio-constructor-src.html

BUG=none

Review URL: https://codereview.chromium.org/36863002

git-svn-id: svn://svn.chromium.org/blink/trunk@160333 bbb929c8-8fbe-4397-9dbb-9b2b20218538