Make Cache Storage tests resilient to execution order

third_party/WebKit/LayoutTests/http/tests/cachestorage/resources/test-helpers.js

 (function() {
   var next_cache_index = 1;
 
   // Returns a promise that resolves to a newly created Cache object. The
   // returned Cache will be destroyed when |test| completes.
   function create_temporary_cache(test) {
     var uniquifier = String(++next_cache_index);
     var cache_name = self.location.pathname + '/' + uniquifier;
 
     test.add_cleanup(function() {
@@ skipping 274 matching lines @@
 function assert_request_in_array(actual, expected_array, description) {
     assert_true(expected_array.some(function(element) {
         try {
             assert_request_equals(actual, element);
             return true;
         } catch (e) {
             return false;
         }
     }), description);
 }
+
+// Deletes all caches, returning a promise indicating success.
+function delete_all_caches() {
+  return self.caches.keys()
+    .then(function(keys) {
+      return Promise.all(keys.map(self.caches.delete.bind(self.caches)));
+    });
+}