Introduce TestSyncUserSettings

It's a simple test implementation of SyncUserSettings that mostly
forwards calls to the TestSyncService. It is not actually used yet, but
it unlocks the migration of tests over to SyncUserSettings.

Bug: 884159
Change-Id: Id9d9c03f639c6523bb6d6592517ba46d1f8f4566
Reviewed-on: https://chromium-review.googlesource.com/c/1335565
Commit-Queue: Marc Treib <[email protected]>
Reviewed-by: Mikel Astiz <[email protected]>
Cr-Commit-Position: refs/heads/master@{#608286}
diff --git a/components/browser_sync/sync_user_settings_impl.h b/components/browser_sync/sync_user_settings_impl.h
index 394f0ccc..59bc7639 100644
--- a/components/browser_sync/sync_user_settings_impl.h
+++ b/components/browser_sync/sync_user_settings_impl.h
@@ -21,7 +21,7 @@
  public:
   // Both |service| and |prefs| must not be null, and must outlive this object.
   SyncUserSettingsImpl(ProfileSyncService* service, syncer::SyncPrefs* prefs);
-  ~SyncUserSettingsImpl();
+  ~SyncUserSettingsImpl() override;
 
   bool IsSyncRequested() const override;
   void SetSyncRequested(bool requested) override;