Add check for zero-sized source YUV + tests.

Took the time to clean up said tests for improved coverage.

BUG=90173
TEST=media_unittests

Review URL: http://codereview.chromium.org/7794016

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@99113 0039d316-1c4b-4281-b951-d872f2087c98