Expose WebCrypto's lookupAlgorithmInfo.

Will allow reuse of this function in the implementation of the enterprise.platfromKeys Chrome extension API.

BUG=364435

Review URL: https://codereview.chromium.org/312393004

git-svn-id: svn://svn.chromium.org/blink/trunk@176190 bbb929c8-8fbe-4397-9dbb-9b2b20218538