Make Cache Storage tests resilient to execution order

third_party/WebKit/LayoutTests/http/tests/cachestorage/script-tests/cache-storage.js

 if (self.importScripts) {
     importScripts('/resources/testharness.js');
     importScripts('../resources/test-helpers.js');
 }
 
 promise_test(function(t) {
     var cache_name = 'cache-storage/foo';
     return self.caches.delete(cache_name)
       .then(function() {
           return self.caches.open(cache_name);
@@ skipping 185 matching lines @@
 promise_test(function(t) {
     return self.caches.delete('cheezburger')
       .then(function(result) {
           assert_false(result,
                        'CacheStorage.delete should return false for a ' +
                        'nonexistent cache.');
         });
   }, 'CacheStorage.delete with nonexistent cache');
 
 promise_test(function(t) {
     var bad_name = 'unpaired\uD800';

[jkarlin, 2016/11/22 15:08:34]

bad_name is very confusing. It makes me think that it's a name that shouldn't
exist. Perhaps call it unpaired_name instead?

[jsbell, 2016/11/22 18:02:39]

Agreed, will do.

-    var converted_name = 'unpaired\uFFFD'; // Don't create cache with this name.
-    return self.caches.has(converted_name)
+    var converted_name = 'unpaired\uFFFD';
+    return Promise.all([
+        self.caches.delete(bad_name),
+        self.caches.delete(converted_name)

[jkarlin, 2016/11/22 15:08:34]

How was this issue (not deleting the caches) not causing flakiness before?

[jsbell, 2016/11/22 18:02:39]

This test runs 3 times (as window, worker, and serviceworker). Normally these
are sharded into 3 different processes, but if the order is randomized they can
end up in the same process; or if you turn off sharding you can make it fail:

run-webkit-tests --no-retry-failures --child-processes=1
http/tests/cachestorage/*/cache-storage.html

[jkarlin, 2016/11/22 18:05:47]

Acknowledged.

+      ])
+      .then(function() {
+          return self.caches.has(converted_name);
+      })
       .then(function(cache_exists) {
           assert_false(cache_exists,
                        'Test setup failure: cache should not exist');
       })
       .then(function() { return self.caches.open(bad_name); })
       .then(function() { return self.caches.keys(); })
       .then(function(keys) {
           assert_true(keys.indexOf(bad_name) !== -1,
                       'keys should include cache with bad name');
       })
       .then(function() { return self.caches.has(bad_name); })
       .then(function(cache_exists) {
           assert_true(cache_exists,
                       'CacheStorage names should be not be converted.');
         })
       .then(function() { return self.caches.has(converted_name); })
       .then(function(cache_exists) {
           assert_false(cache_exists,
                        'CacheStorage names should be not be converted.');
         });
   }, 'CacheStorage names are DOMStrings not USVStrings');
 
 done();