Sync the documentation of seekable() with the MediaSource specification

LayoutTests/http/tests/media/media-source/mediasource-seekable.html

Index: LayoutTests/http/tests/media/media-source/mediasource-seekable.html
diff --git a/LayoutTests/http/tests/media/media-source/mediasource-seekable.html b/LayoutTests/http/tests/media/media-source/mediasource-seekable.html
index 49646f9c2fb51b95cc9ad2ab0186d506e29128a5..cb8def2d0435e55680dedb8dcdc21d8860b84e9d 100644
--- a/LayoutTests/http/tests/media/media-source/mediasource-seekable.html
+++ b/LayoutTests/http/tests/media/media-source/mediasource-seekable.html
@@ -58,7 +58,7 @@
                             assert_equals(mediaElement.buffered.length, 1, 'mediaElement.buffered.length');
                             assert_equals(mediaElement.seekable.start(0), 0);
                             assert_not_equals(mediaElement.seekable.end(0), mediaElement.duration);
-                            assert_not_equals(0, mediaElement.buffered.start(0));
+                            assert_not_equals(mediaElement.seekable.end(0), mediaElement.buffered.start(0));

[Henrik Steen, 2014/11/21 07:46:12]

Hmm..  I would rather (or maybe "also") see a test to assert that
seekable.start(0) isn't equal to buffered.start(0).  This was basically what we
asserted before by saying that seekable.start(0) = 0 != buffered.start(0).

[philipj_slow, 2014/11/21 08:33:38]

Done.

                             assert_equals(mediaElement.seekable.end(0), mediaElement.buffered.end(0));
                             test.done();
                         });