[Sync] Replace manual DI with SetTestingFactory.

components/sync/driver/sync_service.h

Index: components/sync/driver/sync_service.h
diff --git a/components/sync/driver/sync_service.h b/components/sync/driver/sync_service.h
index 1b323b2f5a077b3eff88908d8421c0372764d463..ca749543676b6a7de3649a4ecdd401074540c1d3 100644
--- a/components/sync/driver/sync_service.h
+++ b/components/sync/driver/sync_service.h
@@ -13,6 +13,7 @@
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "base/time/time.h"
+#include "components/keyed_service/core/keyed_service.h"
 #include "components/sync/base/model_type.h"
 #include "components/sync/driver/data_type_encryption_handler.h"
 #include "components/sync/driver/sync_service_observer.h"
@@ -72,7 +73,7 @@ class SyncSetupInProgressHandle {
   base::Closure on_destroy_;
 };
 
-class SyncService : public DataTypeEncryptionHandler {
+class SyncService : public DataTypeEncryptionHandler, public KeyedService {
  public:
   // Used to specify the kind of passphrase with which sync data is encrypted.
   enum PassphraseType {