SafeBrowising: Read and write V4Store from/to disk

components/safe_browsing_db/v4_store.proto

+// 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.
+
+syntax = "proto2";
+
+import "safebrowsing.proto";
+
+option optimize_for = LITE_RUNTIME;
+
+package safe_browsing;
+
+// The message that's serialized to disk when a store update is processed.
+message V4StoreFileFormat {
+  // The magic number to identify this file as a SafeBrowsing hash-prefix file.
+  // https://en.wikipedia.org/wiki/Magic_number_(programming)
+  // Its value is 0x600D71FE
+  optional uint32 magic_number = 1;
+
+  // Identifies the version of the file format.
+  // Version 9 with PVer4 is very different from earlier versions.
+  optional uint32 version_number = 2;
+
+  // Information about the store and the hash-prefix updates.
+  optional FetchThreatListUpdatesResponse.ListUpdateResponse
+      list_update_response = 3;
+}