Adding an MP4 test file for MediaSource layout tests.

This is just the MP4 equilvalent of LayoutTests/http/tests/media/resources/media-source/webm/test.webm

BUG=350209
TBR=adamk@chromium.org

Review URL: https://codereview.chromium.org/189213005

git-svn-id: svn://svn.chromium.org/blink/trunk@168691 bbb929c8-8fbe-4397-9dbb-9b2b20218538