Fix SourceBufferList so SourceBuffer.append() calls are always rejected after the MediaSource is closed.
https://bugs.webkit.org/show_bug.cgi?id=110917

Reviewed by Eric Carlson.

Source/WebCore:

Test: http/tests/media/media-source/video-media-source-reject-append-after-reopening.html

* Modules/mediasource/SourceBufferList.cpp:
(WebCore::SourceBufferList::clear):

LayoutTests:

* http/tests/media/media-source/video-media-source-reject-append-after-reopening-expected.txt: Added.
* http/tests/media/media-source/video-media-source-reject-append-after-reopening.html: Added.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@144203 268f45cc-cd09-0410-ab3c-d52691b4dbfc