[webcrypto] Support 256-bit AES-GCM for OpenSSL implementation.

BUG=386274
R=agl@chromium.org

Review URL: https://codereview.chromium.org/400473003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@284973 0039d316-1c4b-4281-b951-d872f2087c98

content/child/webcrypto/openssl/aes_gcm_openssl.cc

@@ -26,7 +26,8 @@ const EVP_AEAD* GetAesGcmAlgorithmFromKeySize(unsigned int key_size_bytes) {
   switch (key_size_bytes) {
     case 16:
       return EVP_aead_aes_128_gcm();
-    // TODO(eroman): Hook up 256-bit support when it is available.
+    case 32:
+      return EVP_aead_aes_256_gcm();
     default:
       return NULL;
   }

content/child/webcrypto/shared_crypto_unittest.cc

@@ -3286,15 +3286,6 @@ TEST_F(SharedCryptoTest, AesGcmSampleSets) {
     const std::vector<uint8_t> test_cipher_text =
         GetBytesFromHexString(test, "cipher_text");
 
-#if defined(USE_OPENSSL)
-    // TODO(eroman): Add support for 256-bit keys.
-    if (test_key.size() == 32) {
-      LOG(WARNING)
-          << "OpenSSL doesn't support 256-bit keys for AES-GCM; skipping";
-      continue;
-    }
-#endif
-
     blink::WebCryptoKey key = ImportSecretKeyFromRaw(
         test_key,
         CreateAlgorithm(blink::WebCryptoAlgorithmIdAesGcm),