[chromium] Enable the transform-overhang layout tests
They are failing randomly, but all tests pass or fail together it seems. http://test-results.appspot.com/dashboards/flakiness_dashboard.html#showLargeExpectations=true&tests=platform%2Fchromium%2Fcompositing%2Frubberbanding%2Ftransform-overhang-e.html%2Cplatform%2Fchromium%2Fcompositing%2Frubberbanding%2Ftransform-overhang-w.html%2Cplatform%2Fchromium%2Fcompositing%2Frubberbanding%2Ftransform-overhang-n.html%2Cplatform%2Fchromium%2Fcompositing%2Frubberbanding%2Ftransform-overhang-s.html