Update expectations to green the tree.

-Add flaky tests from https://codereview.chromium.org/262963003.
A revert would be tricky.
-Rebaseline fast/transforms/shadows.html as a followup to
https://codereview.chromium.org/279513002.
-Add a flaky imports test.

TBR=loislo@chromium.org,enne@chromium.org,morrita@chromium.org

Review URL: https://codereview.chromium.org/279663002

git-svn-id: svn://svn.chromium.org/blink/trunk@173698 bbb929c8-8fbe-4397-9dbb-9b2b20218538