Implement an initial extension settings API.

chrome/browser/extensions/extension_settings_leveldb_storage.h

Index: chrome/browser/extensions/extension_settings_leveldb_storage.h
diff --git a/chrome/browser/extensions/extension_settings_leveldb_storage.h b/chrome/browser/extensions/extension_settings_leveldb_storage.h
new file mode 100644
index 0000000000000000000000000000000000000000..3e37d59d3d35f442e45bc4e0126fa61bd1f7222b
--- /dev/null
+++ b/chrome/browser/extensions/extension_settings_leveldb_storage.h
@@ -0,0 +1,37 @@
+// Copyright (c) 2011 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_EXTENSIONS_EXTENSION_SETTINGS_LEVELDB_STORAGE_H_
+#define CHROME_BROWSER_EXTENSIONS_EXTENSION_SETTINGS_LEVELDB_STORAGE_H_
+#pragma once
+
+#include "base/scoped_ptr.h"
+#include "chrome/browser/extensions/extension_settings_storage.h"
+#include "third_party/leveldb/include/leveldb/db.h"
+
+// Extension settings storage object, backed by a leveldb database.
+// No caching is done; that should be handled by wrapping with an
+// ExtensionSettingsStorageCache.
+class ExtensionSettingsLeveldbStorage : public ExtensionSettingsStorage {
+ public:
+  // Ownership of db is taken.
+  explicit ExtensionSettingsLeveldbStorage(leveldb::DB* db);
+  ~ExtensionSettingsLeveldbStorage() {}

[dgrogan, 2011/06/18 01:54:40]

I was going to comment that this needs to be deleted on the file thread but I
see that you already covered that :)

Is it kosher to add a DCHECK here to ensure the destructor is indeed run on the
right thread?

[not at google - send to devlin, 2011/06/20 05:33:11]

I don't see why not.  A crash is a crash, whether it's in a destructor or not,
right?

So, Done.

+
+  int type() { return LEVELDB; }
+
+  void Get(const std::string& key, Callback* callback);
+  void Get(const ListValue& keys, Callback* callback);
+  void Get(Callback* callback);
+  void Set(const std::string& key, const Value& value, Callback* callback);
+  void Set(const DictionaryValue& values, Callback* callback);
+  void Remove(const std::string& key, Callback* callback);
+  void Remove(const ListValue& keys, Callback* callback);
+  void Clear(Callback *callback);
+
+ private:
+  scoped_ptr<leveldb::DB> db_;
+};
+
+#endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_SETTINGS_LEVELDB_STORAGE_H_