[webcrypto] Change HMAC key generation length from bytes to bits.

content/child/webcrypto/shared_crypto.cc

 // 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.
 
 #include "content/child/webcrypto/shared_crypto.h"
 
 #include "base/logging.h"
 #include "content/child/webcrypto/crypto_data.h"
 #include "content/child/webcrypto/platform_crypto.h"
 #include "content/child/webcrypto/webcrypto_util.h"
@@ skipping 297 matching lines @@
     case blink::WebCryptoAlgorithmIdAesKw: {
       if (!IsValidAesKeyLengthBits(algorithm.aesKeyGenParams()->lengthBits()))
         return Status::ErrorGenerateKeyLength();
       keylen_bytes = algorithm.aesKeyGenParams()->lengthBits() / 8;
       break;
     }
     case blink::WebCryptoAlgorithmIdHmac: {
       const blink::WebCryptoHmacKeyGenParams* params =
           algorithm.hmacKeyGenParams();
       DCHECK(params);
+#if defined(WEBCRYPTO_HMAC_BITS)
+      if (params->hasLengthBits()) {
+        if (params->optionalLengthBits() % 8)
+          return Status::ErrorGenerateKeyLength();
+        keylen_bytes = params->optionalLengthBits() / 8;
+#else
       if (params->hasLengthBytes()) {
         keylen_bytes = params->optionalLengthBytes();
+#endif
       } else {
         keylen_bytes = ShaBlockSizeBytes(params->hash().id());
         if (keylen_bytes == 0)
           return Status::ErrorUnsupported();
       }
       break;
     }
 
     default:
       return Status::ErrorUnsupported();
@@ skipping 229 matching lines @@
                                          key);
     }
     default:
       return Status::ErrorUnsupported();
   }
 }
 
 }  // namespace webcrypto
 
 }  // namespace content