Defer ARC file system operations while ARC is booting.

components/arc/test/fake_file_system_instance.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 COMPONENTS_ARC_TEST_FAKE_FILE_SYSTEM_INSTANCE_H_
 #define COMPONENTS_ARC_TEST_FAKE_FILE_SYSTEM_INSTANCE_H_
 
 #include <string>
 #include <vector>
 
 #include "base/macros.h"
 #include "components/arc/common/file_system.mojom.h"
 
 namespace arc {
 
+// A fake implementation which returns errors for all requests or just ignores
+// them.
 class FakeFileSystemInstance : public mojom::FileSystemInstance {
  public:
   FakeFileSystemInstance();
 
   // mojom::FileSystemInstance:
   ~FakeFileSystemInstance() override;
 
   void GetChildDocuments(const std::string& authority,
                          const std::string& document_id,
                          const GetChildDocumentsCallback& callback) override;
@@ skipping 10 matching lines @@
 
   void RequestMediaScan(const std::vector<std::string>& paths) override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(FakeFileSystemInstance);
 };
 
 }  // namespace arc
 
 #endif  // COMPONENTS_ARC_TEST_FAKE_FILE_SYSTEM_INSTANCE_H_