Add support for persistent file access in apps.

This replaces chrome.fileSystem.getEntry(By)Id with retainEntry,
restoreEntry and isRestorable, which enable restoring file access after
an app is closed for apps with the fileSystem.retainFiles permission.
Retained files are evicted by LRU, with a maximum of 500 retained files.

BUG=224684

Review URL: https://chromiumcodereview.appspot.com/14607023

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@202276 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 135 insertions, 0 deletions

diff --git a/apps/saved_files_service.h b/apps/saved_files_service.h
new file mode 100644
index 0000000..613764a
--- /dev/null
+++ b/apps/saved_files_service.h
@@ -0,0 +1,135 @@
+// Copyright 2013 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 APPS_SAVED_FILES_SERVICE_H_
+#define APPS_SAVED_FILES_SERVICE_H_
+
+#include <map>
+#include <set>
+#include <string>
+#include <vector>
+
+#include "base/files/file_path.h"
+#include "base/gtest_prod_util.h"
+#include "base/stl_util.h"
+#include "components/browser_context_keyed_service/browser_context_keyed_service.h"
+#include "content/public/browser/notification_observer.h"
+#include "content/public/browser/notification_registrar.h"
+
+class Profile;
+class SavedFilesServiceUnitTest;
+FORWARD_DECLARE_TEST(SavedFilesServiceUnitTest, RetainTwoFilesTest);
+FORWARD_DECLARE_TEST(SavedFilesServiceUnitTest, EvictionTest);
+FORWARD_DECLARE_TEST(SavedFilesServiceUnitTest, SequenceNumberCompactionTest);
+
+namespace extensions {
+class Extension;
+}
+
+namespace apps {
+
+// Represents a file entry that a user has given an app permission to
+// access. Will be persisted to disk (in the Preferences file), so should remain
+// serializable.
+struct SavedFileEntry {
+  SavedFileEntry();
+
+  SavedFileEntry(const std::string& id,
+                 const base::FilePath& path,
+                 bool writable,
+                 int sequence_number);
+
+  // The opaque id of this file entry.
+  std::string id;
+
+  // The path to a file entry that the app had permission to access.
+  base::FilePath path;
+
+  // Whether or not the app had write access to a file entry.
+  bool writable;
+
+  // The sequence number in the LRU of the file entry. The value 0 indicates
+  // that the entry is not in the LRU.
+  int sequence_number;
+};
+
+// Tracks the files that apps have retained access to both while running and
+// when suspended.
+class SavedFilesService : public BrowserContextKeyedService,
+                          public content::NotificationObserver {
+ public:
+  explicit SavedFilesService(Profile* profile);
+  virtual ~SavedFilesService();
+
+  static SavedFilesService* Get(Profile* profile);
+
+  // Registers a file entry with the saved files service, making it eligible to
+  // be put into the queue. File entries that are in the retained files queue at
+  // object construction are automatically registered.
+  void RegisterFileEntry(const std::string& extension_id,
+                         const std::string& id,
+                         const base::FilePath& file_path,
+                         bool writable);
+
+  // If the file with |id| is not in the queue of files to be retained
+  // permanently, adds the file to the back of the queue, evicting the least
+  // recently used entry at the front of the queue if it is full. If it is
+  // already present, moves it to the back of the queue. The |id| must have been
+  // registered.
+  void EnqueueFileEntry(const std::string& extension_id, const std::string& id);
+
+  // Returns whether the file entry with the given |id| has been registered.
+  bool IsRegistered(const std::string& extension_id, const std::string& id);
+
+  // Gets a borrowed pointer to the file entry with the specified |id|. Returns
+  // NULL if the file entry has not been registered.
+  const SavedFileEntry* GetFileEntry(const std::string& extension_id,
+                                     const std::string& id);
+
+  // Returns all registered file entries.
+  std::vector<SavedFileEntry> GetAllFileEntries(
+      const std::string& extension_id);
+
+  // Clears all retained files if the app does not have the
+  // fileSystem.retainFiles permission.
+  void ClearQueueIfNoRetainPermission(const extensions::Extension* extension);
+
+ private:
+  FRIEND_TEST_ALL_PREFIXES(::SavedFilesServiceUnitTest, RetainTwoFilesTest);
+  FRIEND_TEST_ALL_PREFIXES(::SavedFilesServiceUnitTest, EvictionTest);
+  FRIEND_TEST_ALL_PREFIXES(::SavedFilesServiceUnitTest,
+                           SequenceNumberCompactionTest);
+  friend class ::SavedFilesServiceUnitTest;
+
+  // A container for the registered files for an app.
+  class SavedFiles;
+
+  // content::NotificationObserver.
+  virtual void Observe(int type,
+                       const content::NotificationSource& source,
+                       const content::NotificationDetails& details) OVERRIDE;
+
+  // Returns the SavedFiles for |extension_id|, creating it if necessary.
+  SavedFiles* GetOrInsert(const std::string& extension_id);
+
+  // Clears the SavedFiles for |extension_id|.
+  void Clear(const std::string& extension_id);
+
+  static void SetMaxSequenceNumberForTest(int max_value);
+  static void ClearMaxSequenceNumberForTest();
+  static void SetLruSizeForTest(int size);
+  static void ClearLruSizeForTest();
+
+  std::map<std::string, SavedFiles*> extension_id_to_saved_files_;
+  STLValueDeleter<std::map<std::string, SavedFiles*> >
+      extension_id_to_saved_files_deleter_;
+  content::NotificationRegistrar registrar_;
+  Profile* profile_;
+
+  DISALLOW_COPY_AND_ASSIGN(SavedFilesService);
+};
+
+}  // namespace apps
+
+#endif  // APPS_SAVED_FILES_SERVICE_H_