Implement HKDF for WebCrypto (blink-side)

public/platform/WebCryptoKeyAlgorithm.h

Index: public/platform/WebCryptoKeyAlgorithm.h
diff --git a/public/platform/WebCryptoKeyAlgorithm.h b/public/platform/WebCryptoKeyAlgorithm.h
index af0cbc6ff1f7d103c621921024feefa7b061d2a5..74500a56ac6a6108cc75dac9262126ee1b289f81 100644
--- a/public/platform/WebCryptoKeyAlgorithm.h
+++ b/public/platform/WebCryptoKeyAlgorithm.h
@@ -63,6 +63,7 @@ public:
     BLINK_PLATFORM_EXPORT static WebCryptoKeyAlgorithm createHmac(WebCryptoAlgorithmId hash, unsigned keyLengthBits);
     BLINK_PLATFORM_EXPORT static WebCryptoKeyAlgorithm createRsaHashed(WebCryptoAlgorithmId, unsigned modulusLengthBits, const unsigned char* publicExponent, unsigned publicExponentSize, WebCryptoAlgorithmId hash);
     BLINK_PLATFORM_EXPORT static WebCryptoKeyAlgorithm createEc(WebCryptoAlgorithmId, WebCryptoNamedCurve);
+    BLINK_PLATFORM_EXPORT static WebCryptoKeyAlgorithm createKdf(WebCryptoAlgorithmId);
 
     ~WebCryptoKeyAlgorithm() { reset(); }
 
@@ -86,6 +87,7 @@ public:
     BLINK_PLATFORM_EXPORT WebCryptoHmacKeyAlgorithmParams* hmacParams() const;
     BLINK_PLATFORM_EXPORT WebCryptoRsaHashedKeyAlgorithmParams* rsaHashedParams() const;
     BLINK_PLATFORM_EXPORT WebCryptoEcKeyAlgorithmParams* ecParams() const;
+    BLINK_PLATFORM_EXPORT WebCryptoKdfKeyAlgorithmParams* kdfParams() const;

[eroman, 2015/01/07 00:40:31]

Why is this necessary? It looks like your other change was intended for KDF keys
to have no params (which I think makes sense).

[nharper, 2015/01/08 00:58:39]

It was added to make the switch statement in
SerializedScriptValueWriterForModules::writeCryptoKey() to be a little more
consistent, but I agree that it isn't needed (since KDF keys don't have any
params). I've removed it, as I don't think the code symmetry is worth adding
this otherwise useless class.

 
     // Write the algorithm parameters to a dictionary.
     BLINK_PLATFORM_EXPORT void writeToDictionary(WebCryptoKeyAlgorithmDictionary*) const;