Switching nacl trybots to use git checkout.
Switching nacl trybots to use git checkout.


BUG=https://code.google.com/p/chromium/issues/detail?id=401761
TEST=local
R=agable@chromium.org

Review URL: https://codereview.chromium.org/836423003

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@293555 0039d316-1c4b-4281-b951-d872f2087c98

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