Fixes race in Shell

services/catalog/reader.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_READER_H_
 #define SERVICES_CATALOG_READER_H_
 
 #include <memory>
 
 #include "base/callback.h"
 #include "base/files/file_path.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "services/catalog/types.h"
 #include "services/shell/public/interfaces/shell_resolver.mojom.h"
 
 namespace base {
-class TaskRunner;
+class SequencedWorkerPool;
+class SingleThreadTaskRunner;
 }
 
 namespace catalog {
 
 class Entry;
 class ManifestProvider;
 
 // Responsible for loading manifests & building the Entry data structures.
 class Reader {
  public:
   using ReadManifestCallback = base::Callback<void(std::unique_ptr<Entry>)>;
   using CreateEntryForNameCallback =
       base::Callback<void(shell::mojom::ResolveResultPtr)>;
 
-  Reader(base::TaskRunner* file_task_runner,
+  Reader(base::SequencedWorkerPool* worker_pool,
+         ManifestProvider* manifest_provider);
+  Reader(base::SingleThreadTaskRunner* task_runner,
          ManifestProvider* manifest_provider);
   ~Reader();
 
   // Scans the contents of |package_dir|, reading all application manifests and
   // populating |cache|. Runs |read_complete_closure| when done.
   void Read(const base::FilePath& package_dir,
             EntryCache* cache,
             const base::Closure& read_complete_closure);
 
   // Returns an Entry for |mojo_name| via |callback|, assuming a manifest file
   // in the canonical location
   void CreateEntryForName(
       const std::string& mojo_name,
       EntryCache* cache,
       const CreateEntryForNameCallback& entry_created_callback);
 
  private:
+  explicit Reader(ManifestProvider* manifest_provider);
+
   void OnReadManifest(EntryCache* cache,
                       const CreateEntryForNameCallback& entry_created_callback,
                       std::unique_ptr<Entry> entry);
 
   base::FilePath system_package_dir_;
-  base::TaskRunner* file_task_runner_;
+  scoped_refptr<base::TaskRunner> file_task_runner_;
   ManifestProvider* const manifest_provider_;
   base::WeakPtrFactory<Reader> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(Reader);
 };
 
 }  // namespace catalog
 
 #endif  // SERVICES_CATALOG_READER_H_