[webcrypto] Add decrypt() for AES-CBC.

content/renderer/webcrypto/webcrypto_impl.cc

Index: content/renderer/webcrypto/webcrypto_impl.cc
diff --git a/content/renderer/webcrypto/webcrypto_impl.cc b/content/renderer/webcrypto/webcrypto_impl.cc
index 32c0433597e706172482cd8ff56acb9cc4a68739..6eeb3daf5a0cb07de9dc19128ed3e2913338054b 100644
--- a/content/renderer/webcrypto/webcrypto_impl.cc
+++ b/content/renderer/webcrypto/webcrypto_impl.cc
@@ -29,6 +29,20 @@ void WebCryptoImpl::encrypt(
   }
 }
 
+void WebCryptoImpl::decrypt(
+    const WebKit::WebCryptoAlgorithm& algorithm,
+    const WebKit::WebCryptoKey& key,
+    const unsigned char* data,
+    unsigned data_size,
+    WebKit::WebCryptoResult result) {
+  WebKit::WebArrayBuffer buffer;
+  if (!DecryptInternal(algorithm, key, data, data_size, &buffer)) {
+    result.completeWithError();
+  } else {
+    result.completeWithBuffer(buffer);
+  }
+}
+
 void WebCryptoImpl::digest(
     const WebKit::WebCryptoAlgorithm& algorithm,
     const unsigned char* data,