Improve LayoutTest output for Errors

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

Index: LayoutTests/crypto/aes-cbc-parseAlgorithm-failures.html
diff --git a/LayoutTests/crypto/aes-cbc-parseAlgorithm-failures.html b/LayoutTests/crypto/aes-cbc-parseAlgorithm-failures.html
index 4396f831449695a71f031dcd88f131f07b1635c0..fe7e641bce9e8190902701d35d33dbf7c35145a2 100644
--- a/LayoutTests/crypto/aes-cbc-parseAlgorithm-failures.html
+++ b/LayoutTests/crypto/aes-cbc-parseAlgorithm-failures.html
@@ -22,31 +22,32 @@ Promise.resolve(null).then(function(result) {
     var extractable = false;
     var algorithm = {name: 'aes-cbc'};
 
+    debug('\nImporting AES-CBC key...');
     return crypto.subtle.importKey('raw', keyData, algorithm, extractable, usages);
 }).then(function(result) {
     key = result;
 
-    // Bad iv
+    debug('\nencrypt() with iv that is null...');
     return crypto.subtle.encrypt({name: 'AES-CBC', iv: null}, key, data);
 }).then(failAndFinishJSTest, function(result) {
     logError(result);
 
-    // Missing iv
+    debug('\nencrypt() without iv...');
     return crypto.subtle.decrypt({name: 'AES-CBC'}, key, data);
 }).then(failAndFinishJSTest, function(result) {
     logError(result);
 
-    // iv is not a buffer
+    debug('\nencrypt() with iv that is a number...');
     return crypto.subtle.encrypt({name: 'AES-CBC', iv: 3}, key, data);
 }).then(failAndFinishJSTest, function(result) {
     logError(result);
 
-    // iv is too short
+    debug('\nencrypt() with an iv containing 0 bytes...');
     return crypto.subtle.encrypt({name: 'AES-CBC', iv: new Uint8Array(0)}, key, data);
 }).then(failAndFinishJSTest, function(result) {
     logError(result);
 
-    // iv is longer than expected
+    debug('\nencrypt() with an iv containing 17 bytes...');
     return crypto.subtle.encrypt({name: 'AES-CBC', iv: new ArrayBuffer(17)}, key, data);
 }).then(failAndFinishJSTest, function(result) {
     logError(result);