[webcryto] Validate key usages during key creation.

content/child/webcrypto/shared_crypto.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_SHARED_CRYPTO_H_
 #define CONTENT_CHILD_WEBCRYPTO_SHARED_CRYPTO_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
@@ skipping 156 matching lines @@
 }
 
 Status ToPlatformSymKey(const blink::WebCryptoKey& key, platform::SymKey** out);
 
 Status ToPlatformPublicKey(const blink::WebCryptoKey& key,
                            platform::PublicKey** out);
 
 Status ToPlatformPrivateKey(const blink::WebCryptoKey& key,
                             platform::PrivateKey** out);
 
+// Returns Staus::Success() if |usages| is valid for |key_type| and |algorithm|.
+// Otherwise returns a failure
+Status CheckKeyUsages(blink::WebCryptoAlgorithmId algorithm,
+                      blink::WebCryptoKeyType key_type,
+                      blink::WebCryptoKeyUsageMask usages);
+
 }  // namespace webcrypto
 
 }  // namespace content
 
 #endif  // CONTENT_CHILD_WEBCRYPTO_SHARED_CRYPTO_H_