[webcrypto] Reject failed operations with a DOMException rather than null.

LayoutTests/crypto/aes-ctr-parseAlgorithm-failures.html

Index: LayoutTests/crypto/aes-ctr-parseAlgorithm-failures.html
diff --git a/LayoutTests/crypto/aes-ctr-parseAlgorithm-failures.html b/LayoutTests/crypto/aes-ctr-parseAlgorithm-failures.html
index d52f4546b26cdf018cab855f37076513c291b258..7e64d5943945be0226f7e4c07701cd42e7a55a35 100644
--- a/LayoutTests/crypto/aes-ctr-parseAlgorithm-failures.html
+++ b/LayoutTests/crypto/aes-ctr-parseAlgorithm-failures.html
@@ -29,33 +29,27 @@ Promise.resolve(null).then(function(result) {
 
     return crypto.subtle.encrypt({name: 'AES-CTR', counter: null}, key, data);
 }).then(failAndFinishJSTest, function(result) {
-    error = result;
-    shouldBeNull("error");
+    logError(result);
 
     return crypto.subtle.encrypt({name: 'AES-CTR'}, key, data);
 }).then(failAndFinishJSTest, function(result) {
-    error = result;
-    shouldBeNull("error");
+    logError(result);
 
     return crypto.subtle.encrypt({name: 'AES-CTR', counter: new Uint8Array(0)}, key, data);
 }).then(failAndFinishJSTest, function(result) {
-    error = result;
-    shouldBeNull("error");
+    logError(result);
 
     return crypto.subtle.encrypt({name: 'AES-CTR', counter: new Uint8Array(16), length: 256}, key, data);
 }).then(failAndFinishJSTest, function(result) {
-    error = result;
-    shouldBeNull("error");
+    logError(result);
 
     return crypto.subtle.encrypt({name: 'AES-CTR', counter: new Uint8Array(16), length: -3}, key, data);
 }).then(failAndFinishJSTest, function(result) {
-    error = result;
-    shouldBeNull("error");
+    logError(result);
 
     return crypto.subtle.encrypt({name: 'AES-CTR', counter: new Uint8Array(16), length: Infinity}, key, data);
 }).then(failAndFinishJSTest, function(result) {
-    error = result;
-    shouldBeNull("error");
+    logError(result);
 }).then(finishJSTest, failAndFinishJSTest);
 
 </script>