Suppress shadow-drawing.html failure on XP due to text blobs
Suppress shadow-drawing.html failure on XP due to text blobs

This patch suppresses a pixel failure on shadow-drawing.html[1] that
was caused by text blobs being enabled.

[1] http://test-results.appspot.com/dashboards/flakiness_dashboard.html#showExpectations=true&tests=compositing%2Fshadows%2Fshadow-drawing.html

NOTRY=true
TBR=jbroman
BUG=435943

Review URL: https://codereview.chromium.org/752013002

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@185856 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