mediaview: Support watchers in ArcFileSystemOperationRunner.

chrome/browser/chromeos/arc/fileapi/arc_file_system_operation_runner_util.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_FILEAPI_ARC_FILE_SYSTEM_OPERATION_RUNNER_UTIL_H_
 #define CHROME_BROWSER_CHROMEOS_ARC_FILEAPI_ARC_FILE_SYSTEM_OPERATION_RUNNER_UTIL_H_
 
 #include <string>
 
-#include "components/arc/common/file_system.mojom.h"
+#include "base/memory/ref_counted.h"
+#include "chrome/browser/chromeos/arc/fileapi/arc_file_system_operation_runner.h"
 
 class GURL;
 
 namespace arc {
+
+// Wraps an ArcFileSystemOperationRunner::Observer so it is called on the IO
+// thread.
+class ObserverIOThreadWrapper
+    : public base::RefCountedThreadSafe<ObserverIOThreadWrapper>,

[dcheng, 2017/03/02 07:21:45]

Reading through, I'm not quite sure why this is refcounted. It doesn't seem like
any code actually keeps a reference to this, so how is this object supposed to
stay alive?

[Shuhei Takahashi, 2017/03/02 07:30:50]

This object is refcounted because it does not stay in a single fixed thread (UI
and IO).

I added you to R= in https://codereview.chromium.org/2715473003/ which uses this
class actually.

+      public ArcFileSystemOperationRunner::Observer {
+ public:
+  explicit ObserverIOThreadWrapper(
+      ArcFileSystemOperationRunner::Observer* underlying_observer);
+
+  // Disables the observer. After calling this function, the underlying observer
+  // will never be called.
+  // This function should be called on the IO thread.
+  void Disable();
+
+  // ArcFileSystemOperationRunner::Observer overrides:
+  void OnWatchersCleared() override;
+
+ private:
+  friend class base::RefCountedThreadSafe<ObserverIOThreadWrapper>;
+
+  ~ObserverIOThreadWrapper() override;
+
+  void OnWatchersClearedOnIOThread();
+
+  ArcFileSystemOperationRunner::Observer* const underlying_observer_;
+
+  // If set to true, |observer_| will not be called. This variable should be
+  // accessed only on the IO thread.
+  bool disabled_ = false;
+
+  DISALLOW_COPY_AND_ASSIGN(ObserverIOThreadWrapper);
+};
+
 namespace file_system_operation_runner_util {
 
-using GetFileSizeCallback = mojom::FileSystemInstance::GetFileSizeCallback;
+using GetFileSizeCallback = ArcFileSystemOperationRunner::GetFileSizeCallback;
 using OpenFileToReadCallback =
-    mojom::FileSystemInstance::OpenFileToReadCallback;
-using GetDocumentCallback = mojom::FileSystemInstance::GetDocumentCallback;
+    ArcFileSystemOperationRunner::OpenFileToReadCallback;
+using GetDocumentCallback = ArcFileSystemOperationRunner::GetDocumentCallback;
 using GetChildDocumentsCallback =
-    mojom::FileSystemInstance::GetChildDocumentsCallback;
+    ArcFileSystemOperationRunner::GetChildDocumentsCallback;
+using AddWatcherCallback = ArcFileSystemOperationRunner::AddWatcherCallback;
+using RemoveWatcherCallback =
+    ArcFileSystemOperationRunner::RemoveWatcherCallback;
+using WatcherCallback = ArcFileSystemOperationRunner::WatcherCallback;
 
 // Utility functions to post a task to run ArcFileSystemOperationRunner methods.
-// These functions must be called on the IO thread.
+// These functions must be called on the IO thread. Callbacks and observers will
+// be called on the IO thread.
 void GetFileSizeOnIOThread(const GURL& url,
                            const GetFileSizeCallback& callback);
 void OpenFileToReadOnIOThread(const GURL& url,
                               const OpenFileToReadCallback& callback);
 void GetDocumentOnIOThread(const std::string& authority,
                            const std::string& document_id,
                            const GetDocumentCallback& callback);
 void GetChildDocumentsOnIOThread(const std::string& authority,
                                  const std::string& parent_document_id,
                                  const GetChildDocumentsCallback& callback);
+void AddWatcherOnIOThread(const std::string& authority,
+                          const std::string& document_id,
+                          const WatcherCallback& watcher_callback,
+                          const AddWatcherCallback& callback);
+void RemoveWatcherOnIOThread(int64_t watcher_id,
+                             const RemoveWatcherCallback& callback);
+void AddObserverOnIOThread(scoped_refptr<ObserverIOThreadWrapper> observer);
+void RemoveObserverOnIOThread(scoped_refptr<ObserverIOThreadWrapper> observer);
 
 }  // namespace file_system_operation_runner_util
 }  // namespace arc
 
 #endif  // CHROME_BROWSER_CHROMEOS_ARC_FILEAPI_ARC_FILE_SYSTEM_OPERATION_RUNNER_UTIL_H_