Change SourceBuffer.remove() end parameter to unrestricted double.

This change just brings the code in line with the current spec text.

BUG=397769
TEST=LayoutTest/http/tests/media/media-source/mediasource-remove.html

Review URL: https://codereview.chromium.org/453473002

git-svn-id: svn://svn.chromium.org/blink/trunk@179927 bbb929c8-8fbe-4397-9dbb-9b2b20218538