Gardening: rebaseline XP maskRegions.svg; mark a canvas test as flaky.
Gardening: rebaseline XP maskRegions.svg; mark a canvas test as flaky.

BUG=439492,410929
TBR=rtoy@chromium.org

Review URL: https://codereview.chromium.org/788843002

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@186763 bbb929c8-8fbe-4397-9dbb-9b2b20218538

primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs