Refactor the interface for generating keys.

content/child/webcrypto/nss/aes_gcm_nss.cc

Index: content/child/webcrypto/nss/aes_gcm_nss.cc
diff --git a/content/child/webcrypto/nss/aes_gcm_nss.cc b/content/child/webcrypto/nss/aes_gcm_nss.cc
index 9d28a21ca75d6afa09843a02061bdc428615f794..586e307f7b412b413dfc87494893177ca0f039e7 100644
--- a/content/child/webcrypto/nss/aes_gcm_nss.cc
+++ b/content/child/webcrypto/nss/aes_gcm_nss.cc
@@ -153,13 +153,17 @@ class AesGcmImplementation : public AesAlgorithm {
     return AesAlgorithm::VerifyKeyUsagesBeforeImportKey(format, usage_mask);
   }
 
-  virtual Status VerifyKeyUsagesBeforeGenerateKey(
-      blink::WebCryptoKeyUsageMask usage_mask) const override {
+  virtual Status GenerateKey(const blink::WebCryptoAlgorithm& algorithm,
+                             bool extractable,
+                             blink::WebCryptoKeyUsageMask usage_mask,
+                             GenerateKeyResult* result) const override {
     // Prevent generating AES-GCM keys if it is unavailable.
     Status status = NssSupportsAesGcm();
     if (status.IsError())
       return status;
-    return AesAlgorithm::VerifyKeyUsagesBeforeGenerateKey(usage_mask);
+
+    return AesAlgorithm::GenerateKey(
+        algorithm, extractable, usage_mask, result);
   }
 
   virtual Status Encrypt(const blink::WebCryptoAlgorithm& algorithm,