[webcryto] Validate key usages during key creation.

content/child/webcrypto/jwk.cc

Index: content/child/webcrypto/jwk.cc
diff --git a/content/child/webcrypto/jwk.cc b/content/child/webcrypto/jwk.cc
index 53dd787d7a36cc5ebe15fc9aedc7370a1d10aff4..6fd4cc887231da51bfe7ef982a4e10ed650b97c9 100644
--- a/content/child/webcrypto/jwk.cc
+++ b/content/child/webcrypto/jwk.cc
@@ -450,12 +450,6 @@ Status GetOptionalJwkBool(base::DictionaryValue* dict,
   return Status::Success();
 }
 
-// Returns true if the set bits in b make up a subset of the set bits in a.
-bool ContainsKeyUsages(blink::WebCryptoKeyUsageMask a,
-                       blink::WebCryptoKeyUsageMask b) {
-  return (a & b) == b;
-}
-
 // Writes a secret/symmetric key to a JWK dictionary.
 void WriteSecretKey(const std::vector<uint8>& raw_key,
                     base::DictionaryValue* jwk_dict) {