[chromium] Mark canvas-toDataURL-webp.html imageOnlyFailure
https://bugs.webkit.org/show_bug.cgi?id=113169

Unreviewed test expectations update.

Start generating test images on the bots now that libwebp 0.3.0
has landed in chromium webkit.

* platform/chromium/TestExpectations:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@146743 268f45cc-cd09-0410-ab3c-d52691b4dbfc