Modify HttpResponseBodyDrainer for HttpStreamBase
Currently HttpResponseBodyDrainer requires an HttpStream object. But it
works equally well with an HttpStreamBase object, and this permits it to
be used with the new WebSocket implementation.
No functional changes.
This CL is split off from https://codereview.chromium.org/
25417005/
BUG=
TEST=net_unittests
Review URL: https://codereview.chromium.org/
55263004
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232426 0039d316-1c4b-4281-b951-d872f2087c98