WebCrypto: Implement crypto.subtle.deriveKey (chromium-side).

content/child/webcrypto/algorithm_implementation.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_CHILD_WEBCRYPTO_ALGORITHM_IMPLEMENTATION_H_
 #define CONTENT_CHILD_WEBCRYPTO_ALGORITHM_IMPLEMENTATION_H_
 
 #include <stdint.h>
 #include <vector>
 
@@ skipping 63 matching lines @@
 
   // This method corresponds to Web Crypto's crypto.subtle.generateKey().
   //
   // Implementations MUST verify |usages| and return an error if it is not
   // appropriate.
   virtual Status GenerateKey(const blink::WebCryptoAlgorithm& algorithm,
                              bool extractable,
                              blink::WebCryptoKeyUsageMask usages,
                              GenerateKeyResult* result) const;
 
-  // This method corresponds to Web Crypto's "derive bits" operation.
+  // This method corresponds to Web Crypto's "derive bits" operation. It is
+  // essentially crypto.subtle.deriveBits() with the exception that the length
+  // can be "null" (|has_length_bits = true|).
+  //
+  // In cases where the length was not specified, an appropriate default for the
+  // algorithm should be used (as described by the spec).
   virtual Status DeriveBits(const blink::WebCryptoAlgorithm& algorithm,
                             const blink::WebCryptoKey& base_key,
-                            unsigned int length_bits,
+                            bool has_optional_length_bits,
+                            unsigned int optional_length_bits,
                             std::vector<uint8_t>* derived_bytes) const;
 
   // This method corresponds with Web Crypto's "Get key length" operation.
   //
   // In the Web Crypto spec the operation returns either "null" or an
   // "Integer". In this code "null" is represented by setting
   // |*has_length_bits = false|.
   virtual Status GetKeyLength(
       const blink::WebCryptoAlgorithm& key_length_algorithm,
       bool* has_length_bits,
@@ skipping 100 matching lines @@
       blink::WebCryptoKeyUsageMask usages,
       const CryptoData& key_data,
       blink::WebCryptoKey* key) const;
 };
 
 }  // namespace webcrypto
 
 }  // namespace content
 
 #endif  // CONTENT_CHILD_WEBCRYPTO_ALGORITHM_IMPLEMENTATION_H_