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;
+
+  // The rank of the top host.
+  optional int32 rank = 2;

[sclittle, 2016/05/19 01:59:46]

Could you just store these in rank order instead of storing rank here?

[bengr, 2016/05/19 23:19:32]

Done.

+};
+
+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;
+
+  // Count of the total received bytes so far during this precache session.
+  optional uint64 total_bytes = 5;
+
+  // Count of the total received bytes over the network during this precache
+  // session.
+  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 precach
+  // session start time.
+  optional int64 start_time = 8;
+};