[chromium] Disable PNG and ICO image webkit-unit-tests after r139347
https://bugs.webkit.org/show_bug.cgi?id=106631

Reviewed by Eric Seidel.

* tests/WebImageTest.cpp:
(WebKit::TEST): Disable ICOImage and PNGImage tests on WIN and MAC to
green their respective webkit-unit-test bots. The tests still pass on
LINUX so keep test coverage there for now.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@139411 268f45cc-cd09-0410-ab3c-d52691b4dbfc