Use a service to create device management backends.

chrome/test/testing_profile.h

Index: chrome/test/testing_profile.h
diff --git a/chrome/test/testing_profile.h b/chrome/test/testing_profile.h
index 126dfcf66829947435dd7b1f5b6679c35cb7a632..6dc21620515a98ee59288a3b5bc9c8c0f79ffd52 100644
--- a/chrome/test/testing_profile.h
+++ b/chrome/test/testing_profile.h
@@ -308,6 +308,9 @@ class TestingProfile : public Profile {
   virtual ChromeBlobStorageContext* GetBlobStorageContext() { return NULL; }
   virtual ExtensionInfoMap* GetExtensionInfoMap() { return NULL; }
   virtual PromoCounter* GetInstantPromoCounter() { return NULL; }
+  virtual policy::DeviceManagementService* GetDeviceManagementService() {
+    return NULL;
+  }
   virtual policy::DeviceManagementPolicyProvider*
       GetDeviceManagementPolicyProvider() {
     return NULL;