Temporarily suppress canvas-zoom.html test on webkit mac bots.

Will rebaseline upstream.
TBR=rolandsteiner
BUG=none
TEST=none

Review URL: http://codereview.chromium.org/4362002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@64872 0039d316-1c4b-4281-b951-d872f2087c98

webkit/tools/layout_tests/test_expectations.txt

@@ -27,4 +27,5 @@ BUG61411 WIN : inspector/styles-source-lines-inline.html = TEXT
 // Was already marked as flaky on Win, seems to fail on Mac too.
 BUG31342 MAC WIN RELEASE : security/block-test-no-port.html = TEXT PASS
 
+BUGDIMICH MAC : fast/canvas/canvas-zoom.html = IMAGE
 BUGDIMICH MAC : fast/repaint/selection-rl.html = IMAGE