[ServiceWorker] CacheStorage tests.

LayoutTests/http/tests/serviceworker/resources/cache-storage-keys-test-worker.js

+importScripts('worker-test-harness.js');
+
+var test_cache_list =
+  ['', 'example', 'Another cache name', 'A', 'a', 'ex ample'];
+
+promise_test(function(test) {
+    return caches.keys()

[jsbell, 2014/08/15 21:36:13]

Can you write 'self.caches' so it's clear to readers unfamiliar with the spec
that this is referencing a property on the global scope?

[asanka, 2014/08/20 03:10:29]

Done.

+      .then(test.step_func(function(keys) {
+          assert_true(Array.isArray(keys),
+                      'CacheStorage.keys should return an Array.');
+          assert_equals(keys.length, 0,
+                        'CacheStorage.keys should return an empty list for ' +
+                        'a new ServiceWorker.');
+        }))
+
+      .then(function() {
+          return Promise.all(test_cache_list.map(function(key) {
+              return caches.create(key);
+            }));
+        })
+
+      .then(function() { return caches.keys(); })
+      .then(test.step_func(function(keys) {
+          assert_true(Array.isArray(keys),
+                      'CacheStorage.keys should return an Array.');
+          assert_array_equals(keys,
+                              test_cache_list,
+                              'CacheStorage.keys should only return ' +
+                              'existing caches.');
+        }));
+  }, 'CacheStorage keys');