Expose Cache Storage API in global window/worker scope

LayoutTests/http/tests/cachestorage/resources/common-worker.js

Index: LayoutTests/http/tests/cachestorage/resources/common-worker.js
diff --git a/LayoutTests/http/tests/cachestorage/resources/common-worker.js b/LayoutTests/http/tests/cachestorage/resources/common-worker.js
new file mode 100644
index 0000000000000000000000000000000000000000..d0e8544b56c2677a9c60d47a9e8b587d63bc6d6c
--- /dev/null
+++ b/LayoutTests/http/tests/cachestorage/resources/common-worker.js
@@ -0,0 +1,15 @@
+self.onmessage = function(e) {
+    var cache_name = e.data.name;
+
+    self.caches.open(cache_name)
+        .then(function(cache) {
+            return Promise.all([
+                cache.put('https://example.com/a', new Response('a')),
+                cache.put('https://example.com/b', new Response('b')),
+                cache.put('https://example.com/c', new Response('c'))
+            ]);
+        })
+        .then(function() {
+            self.postMessage('ok');
+        });
+};