[XHR] Update note about why the readystatechange event is dispatched multiple times in LOADING state

This behavior was needed when progress was not available (see also this
WebKit bug https://bugs.webkit.org/show_bug.cgi?id=7392). Now we have progress
events. Need to resolve inconsistency between our implemenetation and the
spec by fixing either of them.

BUG=

Review URL: https://codereview.chromium.org/25481002

git-svn-id: svn://svn.chromium.org/blink/trunk@158702 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove npr.org quirk in HTMLMediaElement

This quirk was added in <http://trac.webkit.org/changeset/58586> with
reference to <rdar://problem/7902467>. Unfortunately, the details are
unavailable. It's likely that npr.org has changed since this was added,
so try removing the quirk to see if anything breaks.

BUG=302409

Review URL: https://codereview.chromium.org/25516002

git-svn-id: svn://svn.chromium.org/blink/trunk@158703 bbb929c8-8fbe-4397-9dbb-9b2b20218538