[chromium] Unreviewed gardening. Two webgl/conformance/context tests are timing out.

See https://bugs.webkit.org/show_bug.cgi?id=109114

* platform/chromium/TestExpectations:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@142229 268f45cc-cd09-0410-ab3c-d52691b4dbfc