Reland r45028: Factor out reading and writing of preferences into |PrefStore|.

In order to implement platform-specific policies, reading and writing preferences needs to be abstracted from the |PrefService|. The interface for that is now |PrefStore|, with an implementation |JsonPrefStore|, which stores the pref data in a JSON file. There is another implementation, |DummyPrefStore|, which doesn't store any persistent preferences, and is currently used for tests.

Most of the changes are for using the new interface, which is |new PrefService(new JsonPrefStore(filename))| instead of |new PrefService(filename)|.

BUG=40259
TEST=PrefServiceTest.*:PrefServiceSetValueTest.*:PrefMemberTest.*:JsonPrefStoreTest.*

Review URL: http://codereview.chromium.org/1687001

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@45168 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 46 insertions, 0 deletions

diff --git a/chrome/browser/pref_store.h b/chrome/browser/pref_store.h
new file mode 100644
index 0000000..d7cf8ad
--- /dev/null
+++ b/chrome/browser/pref_store.h
@@ -0,0 +1,46 @@
+// Copyright (c) 2010 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_PREF_STORE_H_
+#define CHROME_BROWSER_PREF_STORE_H_
+
+class DictionaryValue;
+
+// This is an abstract interface for reading and writing from/to a persistent
+// preference store, used by |PrefService|. An implementation using a JSON file
+// can be found in |JsonPrefStore|, while an implementation without any backing
+// store (currently used for testing) can be found in |DummyPrefStore|.
+class PrefStore {
+ public:
+  // Unique integer code for each type of error so we can report them
+  // distinctly in a histogram.
+  // NOTE: Don't change the order here as it will change the server's meaning
+  // of the histogram.
+  enum PrefReadError {
+    PREF_READ_ERROR_NONE = 0,
+    PREF_READ_ERROR_JSON_PARSE,
+    PREF_READ_ERROR_JSON_TYPE,
+    PREF_READ_ERROR_ACCESS_DENIED,
+    PREF_READ_ERROR_FILE_OTHER,
+    PREF_READ_ERROR_FILE_LOCKED,
+    PREF_READ_ERROR_NO_FILE,
+  };
+
+  virtual ~PrefStore() { }
+
+  // Whether the store is in a pseudo-read-only mode where changes are not
+  // actually persisted to disk.  This happens in some cases when there are
+  // read errors during startup.
+  virtual bool ReadOnly() { return true; }
+
+  virtual DictionaryValue* Prefs() = 0;
+
+  virtual PrefReadError ReadPrefs() = 0;
+
+  virtual bool WritePrefs() { return true; }
+
+  virtual void ScheduleWritePrefs() { }
+};
+
+#endif  // CHROME_BROWSER_PREF_STORE_H_