Rebaseline failing animation interpolation tests after test helper change

These tests landed at the same time as a change to the test helper and
started failing:
animations/interpolation/border-image-source-interpolation.html
animations/interpolation/svg-flood-opacity-interpolation.html
animations/interpolation/webkit-mask-box-image-source-interpolation.html
animations/interpolation/webkit-mask-image-interpolation.html
animations/interpolation/webkit-mask-position-interpolation.html

Test helper change:
https://codereview.chromium.org/26979002/

TBR=dstockwell

Review URL: https://codereview.chromium.org/27299002

git-svn-id: svn://svn.chromium.org/blink/trunk@159664 bbb929c8-8fbe-4397-9dbb-9b2b20218538