Enable gatekeeper on chromium.linux and chromium.mac.
Enable gatekeeper on chromium.linux and chromium.mac.

BUG=388845

Review URL: https://codereview.chromium.org/356863002

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@279890 0039d316-1c4b-4281-b951-d872f2087c98

eunchong/build,eunchong/build,eunchong/build,eunchong/build