Refactor a database test such that its code can be shared between the documen...

LayoutTests/storage/resources/database-worker-controller.js

+var databaseWorker = new Worker('resources/database-worker.js');
+
+databaseWorker.onmessage = function(event) {
+  if (event.data.indexOf('log:') == 0) {
+    log(event.data.substring(4));
+  } else if (event.data == 'notifyDone') {
+    if (window.layoutTestController)
+        layoutTestController.notifyDone();
+  } else {
+    throw new Error("Unrecognized message: " + event);
+  }
+}
+
+function log(message)
+{
+    document.getElementById("console").innerText += message + "\n";
+}
+