Narrow down failure expectations for inspector/device-emulation tests

TBR=apavlov,dstockwell
BUG=304841

Review URL: https://codereview.chromium.org/135923003

git-svn-id: svn://svn.chromium.org/blink/trunk@165062 bbb929c8-8fbe-4397-9dbb-9b2b20218538