Enable the sandbox on Linux where it is present and ready.
Enable the sandbox on Linux where it is present and ready.

R=maruel@chromium.org,szager@chromium.org
BUG=126163


Review URL: https://chromiumcodereview.appspot.com/10411027

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@137969 0039d316-1c4b-4281-b951-d872f2087c98

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