Update test_expectations.txt
Update test_expectations.txt

fast/canvas-empty-image-pattern.html passes since WebKit r58480:r58515 (win), r58439 (linux) and never failed on mac according flakiness_dashboard

BUG=none
TEST=none
RBT=agl

Review URL: http://codereview.chromium.org/1692018

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@46051 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser