Add pause/resume functionality to precache

components/precache/core/proto/unfinished_work.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 "precache.proto";
+
+package precache;
+
+// Chrome requires this.
+option optimize_for = LITE_RUNTIME;
+
+message TopHost {
+  // The host name of a top host.
+  optional string hostname = 1;
+};
+
+message PrecacheManifestURL {
+  // The URL that provides a manifest.
+  optional string url = 1;
+};
+
+// Information about the precache work that needs to be completed.
+message PrecacheUnfinishedWork {
+  // Top hosts for which to fetch manifests.
+  repeated TopHost top_host = 1;
+
+  optional PrecacheConfigurationSettings config_settings = 2;
+
+  // Manifest URLs remaining to be fetched.
+  repeated PrecacheManifestURL manifest = 3;
+
+  // Resource URLs remaining to be fetched.
+  repeated PrecacheResource resource = 4;
+
+  // Tally of the total number of bytes contained in URL fetches, including
+  // config, manifests, and resources. This the number of bytes as they would be
+  // compressed over the network.
+  optional uint64 total_bytes = 5;
+
+  // Tally of the total number of bytes received over the network from URL
+  // fetches (the same ones as in total_response_bytes_). This includes response
+  // headers and intermediate responses such as 30xs.
+  optional uint64 network_bytes = 6;
+
+  // The total number of manifest URLs that the precache session started with.
+  optional uint64 num_manifest_urls = 7;
+
+  // The internal value of a base::Time object representing the precache
+  // session start time. The start time is the time just before when top hosts
+  // are requested.
+  optional int64 start_time = 8;
+};