Update geofencing layout tests to use mock service.

LayoutTests/http/tests/geofencing/resources/worker-passes-events-back.js

Index: LayoutTests/http/tests/geofencing/resources/worker-passes-events-back.js
diff --git a/LayoutTests/http/tests/geofencing/resources/worker-passes-events-back.js b/LayoutTests/http/tests/geofencing/resources/worker-passes-events-back.js
new file mode 100644
index 0000000000000000000000000000000000000000..c8dc9aed754a05cd1e656103ff8ed56cc2754588
--- /dev/null
+++ b/LayoutTests/http/tests/geofencing/resources/worker-passes-events-back.js
@@ -0,0 +1,14 @@
+var port;
+
+self.addEventListener('message', function(event) {
+  port = event.data.port;
+  port.postMessage('setup');
+});
+
+self.addEventListener('geofenceenter', function(event) {
+  port.postMessage({event: 'geofenceenter', id: event.region.id});
+});
+
+self.addEventListener('geofenceleave', function(event) {
+  port.postMessage({event: 'geofenceleave', id: event.region.id});
+});