Make browser tests all run from a server instead of the local filesystem.

samples/swarm/SwarmApp.dart

Index: samples/swarm/SwarmApp.dart
diff --git a/samples/swarm/SwarmApp.dart b/samples/swarm/SwarmApp.dart
index 462dcd30572f275598f2606665abc1458e343606..aa293cb602e9a73695189ba913d8365e1590e999 100644
--- a/samples/swarm/SwarmApp.dart
+++ b/samples/swarm/SwarmApp.dart
@@ -23,8 +23,8 @@ class Swarm extends App {
   /** Observable UI state. */
   SwarmState state;
 
-  Swarm() : super(), onLoadFired = false {
-    Sections.initializeFromUrl((currSections) {
+  Swarm({bool useCannedData : false}) : super(), onLoadFired = false {
+    Sections.initializeFromUrl(useCannedData, (currSections) {
       sections = currSections;
       state = new SwarmState(sections);
       setupApp();