Add support for an optional "requirements" section in extension/app manifests.

The expected format is:

"requirements": {
  "requirement1": {
    // requirement details
  },
  "requiement2": {
    // requirement details
  },
  ...
}

Only validation and whitelisting for hosted apps is done, for now only the web
store will use requirements data.

BUG=99241
R=yoz@chromium.org

Review URL: http://codereview.chromium.org/8200015

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@104582 0039d316-1c4b-4281-b951-d872f2087c98
7 files changed