We don't currently expose the Crypto constructor on the global object. The spec, https://dvcs.w3.org/hg/webcrypto-api/raw-file/tip/spec/Overview.html#crypto-interface, doesn't say we should exclude it, so we shouldn't be.
<rdar://problem/25584034>
Created attachment 275823 [details] Patch
Comment on attachment 275823 [details] Patch r=me!
Committed r199159: <http://trac.webkit.org/changeset/199159>