[webcrypto] Update layout tests to match idl generator changes.

LayoutTests/crypto/digest-failures.html

Index: LayoutTests/crypto/digest-failures.html
diff --git a/LayoutTests/crypto/digest-failures.html b/LayoutTests/crypto/digest-failures.html
index c760cd06c4801c21731b3f94134f27ad6078d320..954e70010212d1f83f06a91f385316a358cc94a9 100644
--- a/LayoutTests/crypto/digest-failures.html
+++ b/LayoutTests/crypto/digest-failures.html
@@ -13,10 +13,13 @@ description("Tests incorrect calls to crypto.subtle.digest()");
 
 jsTestIsAsync = true;
 
-// Called with too few parameters.
-shouldThrow("crypto.subtle.digest({name: 'sha-1'})");
-
 Promise.resolve(null).then(function(result) {
+    // Called with too few parameters.
+    return crypto.subtle.digest({name: 'sha-1'});
+}).then(failAndFinishJSTest, function(result) {
+    error = result;
+    shouldBeTypeError("error");
+
     // "null" is not a valid data argument.
     return crypto.subtle.digest({name: 'sha-1'}, null);
 }).then(failAndFinishJSTest, function(result) {