[webcrypto] Check for empty key usages *after* key creation rather than before, to match the spec's…

components/webcrypto/algorithms/secret_key_util.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 COMPONENTS_WEBCRYPTO_ALGORITHMS_SECRET_KEY_UTIL_
 #define COMPONENTS_WEBCRYPTO_ALGORITHMS_SECRET_KEY_UTIL_
 
 #include <stdint.h>
 
 #include <string>
@@ skipping 23 matching lines @@
 
 // Creates a WebCrypto secret key given the raw data. The provided |key_data|
 // will be copied into the new key. This function does not do any validation
 // checks for the provided parameters.
 Status CreateWebCryptoSecretKey(const CryptoData& key_data,
                                 const blink::WebCryptoKeyAlgorithm& algorithm,
                                 bool extractable,
                                 blink::WebCryptoKeyUsageMask usages,
                                 blink::WebCryptoKey* key);
 
-// Checks that |actual_usages| is a non-empty subset of |all_possible_usages|.
-Status CheckSecretKeyCreationUsages(
-    blink::WebCryptoKeyUsageMask all_possible_usages,
-    blink::WebCryptoKeyUsageMask actual_usages);
-
 // Writes a JWK-formatted symmetric key to |jwk_key_data|.
 //  * raw_key_data: The actual key data
 //  * algorithm: The JWK algorithm name (i.e. "alg")
 //  * extractable: The JWK extractability (i.e. "ext")
 //  * usages: The JWK usages (i.e. "key_ops")
 void WriteSecretKeyJwk(const CryptoData& raw_key_data,
                        const std::string& algorithm,
                        bool extractable,
                        blink::WebCryptoKeyUsageMask usages,
                        std::vector<uint8_t>* jwk_key_data);
 
 // Parses a UTF-8 encoded JWK (key_data), and extracts the key material to
 // |*raw_key_data|. Returns Status::Success() on success, otherwise an error.
 // In order for this to succeed:
 //   * expected_extractable must be consistent with the JWK's "ext", if
 //     present.
 //   * expected_usages must be a subset of the JWK's "key_ops" if present.
 Status ReadSecretKeyNoExpectedAlgJwk(
     const CryptoData& key_data,
     bool expected_extractable,
     blink::WebCryptoKeyUsageMask expected_usages,
     std::vector<uint8_t>* raw_key_data,
     JwkReader* jwk);
 
 }  // namespace webcrypto
 
 #endif  // COMPONENTS_WEBCRYPTO_ALGORITHMS_SECRET_KEY_UTIL_