Revert of arc: Fix thread unsafe behavior of ArcDownloadsWatcherService

chrome/browser/chromeos/arc/arc_downloads_watcher_service.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 CHROME_BROWSER_CHROMEOS_ARC_ARC_DOWNLOADS_WATCHER_SERVICE_H_
 #define CHROME_BROWSER_CHROMEOS_ARC_ARC_DOWNLOADS_WATCHER_SERVICE_H_
 
 #include <memory>
 #include <vector>
 
@@ skipping 23 matching lines @@
   // InstanceHolder<mojom::FileSystemInstance>::Observer
   void OnInstanceReady() override;
   void OnInstanceClosed() override;
 
  private:
   class DownloadsWatcher;
 
   void StartWatchingDownloads();
   void StopWatchingDownloads();
 
-  void OnDownloadsChanged(mojo::Array<mojo::String> paths);
+  void OnDownloadsChanged(const std::vector<base::FilePath>& paths);
 
   std::unique_ptr<DownloadsWatcher> watcher_;
 
   // Note: This should remain the last member so it'll be destroyed and
   // invalidate the weak pointers before any other members are destroyed.
   base::WeakPtrFactory<ArcDownloadsWatcherService> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ArcDownloadsWatcherService);
 };
 
 }  // namespace arc
 
 #endif  // CHROME_BROWSER_CHROMEOS_ARC_ARC_DOWNLOADS_WATCHER_SERVICE_H_