[webcrypto] Don't throw any extra WebIDL exceptions from WebCrypto methods.

LayoutTests/crypto/wrapKey-badParameters.html

Index: LayoutTests/crypto/wrapKey-badParameters.html
diff --git a/LayoutTests/crypto/wrapKey-badParameters.html b/LayoutTests/crypto/wrapKey-badParameters.html
index 7130d0f17ac59e40729fd7a751f42a44e50006a0..21029e3b8a8e216648a8d7e9cb0cc68789e3a240 100644
--- a/LayoutTests/crypto/wrapKey-badParameters.html
+++ b/LayoutTests/crypto/wrapKey-badParameters.html
@@ -40,13 +40,22 @@ importWrappingKey().then(function(result) {
     wrapAlgorithm = {name: 'aes-cbc', iv: new Uint8Array(16)};
 
     // Invalid key
-    shouldThrow("crypto.subtle.wrapKey('raw', 1, wrappingKey, wrapAlgorithm)");
+    return crypto.subtle.wrapKey('raw', 1, wrappingKey, wrapAlgorithm);
+}).then(failAndFinishJSTest, function(result) {
+    error = result;
+    shouldBeNull("error");
 
     // Invalid wrappingKey
-    shouldThrow("crypto.subtle.wrapKey('raw', key, '', wrapAlgorithm)");
+    return crypto.subtle.wrapKey('raw', key, '', wrapAlgorithm);
+}).then(failAndFinishJSTest, function(result) {
+    error = result;
+    shouldBeNull("error");
 
     // Invalid wrapAlgorithm
-    shouldThrow("crypto.subtle.wrapKey('raw', key, wrappingKey, undefined)");
+    return crypto.subtle.wrapKey('raw', key, wrappingKey, undefined);
+}).then(failAndFinishJSTest, function(result) {
+    error = result;
+    shouldBeNull("error");
 
     // Invalid format for wrapKey
     return crypto.subtle.wrapKey('bad-format', key, wrappingKey, wrapAlgorithm);