[GCM] Observe the event listener adding such that GCM can be started

chrome/browser/services/gcm/gcm_profile_service_unittest.cc

Index: chrome/browser/services/gcm/gcm_profile_service_unittest.cc
diff --git a/chrome/browser/services/gcm/gcm_profile_service_unittest.cc b/chrome/browser/services/gcm/gcm_profile_service_unittest.cc
index 2ab485a2f1d747799765a696d211908c4ed47b0c..1ac5a618dc309b6f9225c5db820664b52e8b4cfd 100644
--- a/chrome/browser/services/gcm/gcm_profile_service_unittest.cc
+++ b/chrome/browser/services/gcm/gcm_profile_service_unittest.cc
@@ -29,6 +29,8 @@
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/test/test_browser_thread_bundle.h"
+#include "extensions/browser/event_router.h"
+#include "extensions/browser/extension_prefs.h"
 #include "extensions/common/extension.h"
 #include "extensions/common/manifest_constants.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -283,6 +285,12 @@ class GCMProfileServiceTestConsumer : public GCMProfileService::TestingDelegate{
         CommandLine::ForCurrentProcess(), base::FilePath(), false);
     extension_service_ = extension_system->Get(profile())->extension_service();
 
+    // EventRouter is needed for GcmJsEventRouter.
+    if (!extension_system->event_router()) {
+      extension_system->SetEventRouter(scoped_ptr<EventRouter>(
+          new EventRouter(profile(), ExtensionPrefs::Get(profile()))));
+    }
+
     // Enable GCM such that tests could be run on all channels.
     profile()->GetPrefs()->SetBoolean(prefs::kGCMChannelEnabled, true);