Expose Cache Storage API in global window/worker scope

LayoutTests/http/tests/cachestorage/script-tests/cache-storage-match.js

-importScripts('worker-testharness.js');
-importScripts('../../resources/testharness-helpers.js');
-importScripts('override_assert_object_equals.js');
+if (self.importScripts) {
+    importScripts('/resources/testharness.js');
+    importScripts('/resources/testharness-helpers.js');
+    importScripts('../resources/test-helpers.js');
+}
 
 (function() {
   var next_index = 1;
 
   // Returns a transaction (request, response, and url) for a unique URL.
   function create_unique_transaction(test) {
     var uniquifier = String(next_index++);
     var url = 'http://example.com/' + uniquifier;
 
     return {
@@ skipping 96 matching lines @@
         })
       .then(function(response) {
           assert_equals(response, undefined,
                         'The response should not be found.');
           return self.caches.has('foo');
         })
       .then(function(has_foo) {
           assert_false(has_foo, "The cache should still not exist.");
         })
 }, 'CacheStorageMatch with no caches available but name provided');
+
+done();