Add some media layout tests to SmokeTests.

BUG=315949
TEST=These tests pass on Nexus 7 v2 and are pretty fast.

Review URL: https://codereview.chromium.org/61723004

git-svn-id: svn://svn.chromium.org/blink/trunk@161495 bbb929c8-8fbe-4397-9dbb-9b2b20218538