WebCrypto: Implement importKey() and sign() for HMAC in NSS

BUG=245025
R=eroman@chromium.org,ellyjones@chromium.org

Review URL: https://chromiumcodereview.appspot.com/23569007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@223506 0039d316-1c4b-4281-b951-d872f2087c98
5 files changed