[ServiceWorker] CacheStorage tests.

LayoutTests/http/tests/serviceworker/resources/interfaces-worker.js

 importScripts('interfaces.js');
 importScripts('worker-test-harness.js');
 
 test(function() {
     var EVENT_HANDLER = 'object';
 
     verifyInterface('ServiceWorkerGlobalScope',
                     self,
                     {
                         scope: 'string',
                         clients: 'object',
                         close: 'function',
 
                         onactivate: EVENT_HANDLER,
                         onfetch: EVENT_HANDLER,
                         oninstall: EVENT_HANDLER,
                         onmessage: EVENT_HANDLER
                     });
 
     verifyInterface('ServiceWorkerClients',
                     self.clients,
                     {
                         getAll: 'function'
                     });
 
     verifyInterface('ServiceWorkerClient');
     // FIXME: Get an instance and test it, or ensure property exists on prototype.
 
-}, 'Interfaces and attributes in ServiceWorkerGlobalScope');
+    verifyInterface('CacheStorage',
+                    self.caches,
+                    {
+                      match: 'function',
+                      get: 'function',
+                      has: 'function',
+                      create: 'function',
+                      delete: 'function',
+                      keys: 'function'
+                    });
+  }, 'Interfaces and attributes in ServiceWorkerGlobalScope');