[ServiceWorker] CacheStorage tests.

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

+importScripts('worker-test-harness.js');
+
+var test_cache_list = ['enum-1', 'enum-2', 'enum-3'];

[dominicc (has gone to gerrit), 2014/08/11 01:57:36]

Is it worth including interesting names like empty string or ones that differ by
whitespace?

[asanka, 2014/08/13 01:22:51]

Added some variants. It shouldn't hurt, but the resulting errors may not be very
specific. If there are important special cases we'd want to add those to
cache-storage-test-worker.

+
+promise_test(function(test) {
+    return caches.keys()
+      .then(test.step_func(function(keys) {
+          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');

[dominicc (has gone to gerrit), 2014/08/11 01:57:36]

There's inconsistency about ending with a period. From memory one is right,
because the test harness cooks up a failure string. At least end with a period
for consistency with the above two.

[asanka, 2014/08/13 01:22:51]

I added a '.'. The string put together by the test harness look like
"<description> <error message>" where <error message> is often a verb phrase but
not consistently so. Even if it were I'm not sure how well we'd be able to
phrase every test description as a subject while still leaving the code
comprehensible.

+        }));
+  }, 'CacheStorage keys');