delete the levelDB storage implementation.

components/offline_pages/proto/offline_pages.proto

-// Copyright 2015 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.
-//
-// Offline page item protocol for storage and exchanging of offline page
-// metadata.
-
-syntax = "proto2";
-
-option optimize_for = LITE_RUNTIME;
-option retain_unknown_fields = true;
-
-package offline_pages;
-
-message OfflinePageEntry {
-  // URL of the offline page.
-  optional string url = 1;
-
-  // Bookmark ID of the offline page, this is deprecated in favor of the
-  // more generic ClientID below.  No new pages should have this field.
-  optional int64 deprecated_bookmark_id = 2 [default = -1];
-
-  // Offline ID of the page.  Every page entry has a unique offline_id.
-  optional int64 offline_id = 10;
-
-  // Version of the offline page metadata.
-  optional int32 version = 3;
-
-  // Path to the offline archive.
-  optional string file_path = 4;
-
-  // Size of the offline archive.
-  optional int64 file_size = 5;
-
-  // Creation time of the offline archive.
-  optional int64 creation_time = 6;
-
-  // Last access time of the offline archive.
-  optional int64 last_access_time = 7;
-
-  // Number of times that the offline archive has been accessed.
-  optional int32 access_count = 8;
-
-  // Flags about the state and behavior of the offline page.
-  enum Flags {
-    // No flag is set.
-    NONE = 0;
-    // Indicates that the page is marked for deletion. The real deletion will
-    // occur soon, after which the undo will not be possible.
-    MARKED_FOR_DELETION = 1;
-  };
-
-  // Flags for the offline page.
-  optional Flags flags = 9;
-
-  // Information about this offline page in the namespace/id of the client that
-  // requested that it be saved. Useful for reverse lookups.
-
-  // Namespace (e.g. client name) to separate the (possibly identical) ids
-  // from two different clients.
-  optional string client_id_name_space = 11;
-  // Identifier that has meaning for clients of the offline page API.
-  // This is provided by consumers of the offline pages API and is opaque to us.
-  optional string client_id = 12;
-}