Add initial Controller to DownloadService

components/download/internal/model_impl.h

Index: components/download/internal/model_impl.h
diff --git a/components/download/internal/model_impl.h b/components/download/internal/model_impl.h
index 8c78501956619523935d6b5e37cab4ce2cbbd636..485b85d5dcae2a97556e2aa65db223d4188750d9 100644
--- a/components/download/internal/model_impl.h
+++ b/components/download/internal/model_impl.h
@@ -23,11 +23,11 @@ struct Entry;
 // The internal implementation of Model.
 class ModelImpl : public Model {
  public:
-  ModelImpl(Client* client, std::unique_ptr<Store> store);
+  ModelImpl(std::unique_ptr<Store> store);
   ~ModelImpl() override;
 
   // Model implementation.
-  void Initialize() override;
+  void Initialize(Client* client) override;
   void Destroy() override;
   void Add(const Entry& entry) override;
   void Update(const Entry& entry) override;
@@ -53,7 +53,7 @@ class ModelImpl : public Model {
 
   // The external Model::Client reference that will receive all interesting
   // Model notifications.
-  Client* const client_;
+  Client* client_;
 
   // The backing Store that is responsible for saving and loading the
   // persisted entries.