Send the list of used and unused resources for precache

components/precache/core/proto/unfinished_work.proto

Index: components/precache/core/proto/unfinished_work.proto
diff --git a/components/precache/core/proto/unfinished_work.proto b/components/precache/core/proto/unfinished_work.proto
index deb6329bbf6c627820cbd379e62312b5da9ecd18..5651bbb8d5e3068b559c5c015c53c6f65fa6d678 100644
--- a/components/precache/core/proto/unfinished_work.proto
+++ b/components/precache/core/proto/unfinished_work.proto
@@ -16,7 +16,7 @@ message TopHost {
   optional string hostname = 1;
 };
 
-message PrecacheManifestURL {
+message DeprecatedPrecacheManifestURL {
   // The URL that provides a manifest.
   optional string url = 1;
 };
@@ -28,8 +28,9 @@ message PrecacheUnfinishedWork {
 
   optional PrecacheConfigurationSettings config_settings = 2;
 
-  // Manifest URLs remaining to be fetched.
-  repeated PrecacheManifestURL manifest = 3;
+  // DEPRECATED: Manifest URLs remaining to be fetched.
+  repeated DeprecatedPrecacheManifestURL deprecated_manifest = 3
+      [deprecated = true];
 
   // Resource URLs remaining to be fetched.
   repeated PrecacheResource resource = 4;