Add digestSynchronous WebCrypto method.

public/platform/WebCrypto.h

Index: public/platform/WebCrypto.h
diff --git a/public/platform/WebCrypto.h b/public/platform/WebCrypto.h
index 998a2153ec8165ddf0a17896085ff8d2873a2920..18103fe79a0956a695f90cd579dd0ce6c1183389 100644
--- a/public/platform/WebCrypto.h
+++ b/public/platform/WebCrypto.h
@@ -178,6 +178,13 @@ public:
     // It is possible that unwrappedKeyAlgorithm.isNull()
     virtual void unwrapKey(WebCryptoKeyFormat, const unsigned char* wrappedKey, unsigned wrappedKeySize, const WebCryptoKey&, const WebCryptoAlgorithm& unwrapAlgorithm, const WebCryptoAlgorithm& unwrappedKeyAlgorithm, bool extractable, WebCryptoKeyUsageMask, WebCryptoResult result) { result.completeWithError(); }
 
+    // This is the one exception to the "Completing the request" guarantees
+    // outlined above. digestSynchronous must provide the result into result
+    // synchronously. It must return |true| on successful calculation of the
+    // digest and |false| otherwise. This is useful for Blink internal crypto
+    // and is not part of the WebCrypto standard.
+    virtual bool digestSynchronous(const WebCryptoAlgorithm&, const unsigned char* data, unsigned dataSize, WebArrayBuffer& result) { return false; }

[eroman, 2014/02/08 01:40:22]

* Pass a WebCryptoAlgorithmId instead (since none of the supported digests have
any parameters, and constructing WebCryptoAlgorithm is clumsy

* I think WebVector would be a more appropriate output type.

[jww, 2014/02/08 02:31:18]

Done.
I'm happy to do this if you think it's best, but given that it's a
WebArrayBuffer everywhere else, it seems a bit inconsistent to start using
WebVectors here (and it's a simple conversion to WebVector for the consumer if
they choose to use it). Let me know either way.

+
 protected:
     virtual ~WebCrypto() { }
 };