Fixes race in Shell

services/catalog/catalog.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef SERVICES_CATALOG_CATALOG_H_
 #define SERVICES_CATALOG_CATALOG_H_
 
 #include <map>
 #include <memory>
 #include <string>
 
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "mojo/public/cpp/bindings/binding.h"
 #include "services/catalog/public/interfaces/catalog.mojom.h"
 #include "services/catalog/types.h"
 #include "services/shell/public/cpp/shell_client.h"
 #include "services/shell/public/interfaces/shell_client.mojom.h"
 #include "services/shell/public/interfaces/shell_resolver.mojom.h"
 
 namespace base {
-class TaskRunner;
+class SequencedWorkerPool;
+class SingleThreadTaskRunner;
 }
 
 namespace shell {
 class ShellConnection;
 }
 
 namespace catalog {
 
 class Instance;
 class ManifestProvider;
 class Reader;
 class Store;
 
 // Creates and owns an instance of the catalog. Exposes a ShellClientPtr that
 // can be passed to the Shell, potentially in a different process.
 class Catalog : public shell::ShellClient,
                 public shell::InterfaceFactory<mojom::Catalog>,
                 public shell::InterfaceFactory<shell::mojom::ShellResolver> {
  public:
   // |manifest_provider| may be null.
-  Catalog(base::TaskRunner* file_task_runner,
+  Catalog(base::SequencedWorkerPool* worker_pool,
+          std::unique_ptr<Store> store,
+          ManifestProvider* manifest_provider);
+  Catalog(base::SingleThreadTaskRunner* task_runner,
           std::unique_ptr<Store> store,
           ManifestProvider* manifest_provider);
   ~Catalog() override;
 
   shell::mojom::ShellClientPtr TakeShellClient();
 
  private:
+  explicit Catalog(std::unique_ptr<Store> store);
+
+  // Starts a scane for system packages.
+  void ScanSystemPackageDir();
+
   // shell::ShellClient:
   bool AcceptConnection(shell::Connection* connection) override;
 
   // shell::InterfaceFactory<shell::mojom::ShellResolver>:
   void Create(shell::Connection* connection,
               shell::mojom::ShellResolverRequest request) override;
 
   // shell::InterfaceFactory<mojom::Catalog>:
   void Create(shell::Connection* connection,
               mojom::CatalogRequest request) override;
 
   Instance* GetInstanceForUserId(const std::string& user_id);
 
   void SystemPackageDirScanned();
 
-  base::TaskRunner* const file_task_runner_;
   std::unique_ptr<Store> store_;
 
   shell::mojom::ShellClientPtr shell_client_;
   std::unique_ptr<shell::ShellConnection> shell_connection_;
 
   std::map<std::string, std::unique_ptr<Instance>> instances_;
 
   std::unique_ptr<Reader> system_reader_;
   EntryCache system_cache_;
   bool loaded_ = false;
 
   base::WeakPtrFactory<Catalog> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(Catalog);
 };
 
 }  // namespace catalog
 
 #endif  // SERVICES_CATALOG_CATALOG_H_