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..700db23dfdc0d287188b0c485dd8f1310e614b1d 100644
--- a/components/precache/core/proto/unfinished_work.proto
+++ b/components/precache/core/proto/unfinished_work.proto
@@ -16,11 +16,6 @@ message TopHost {
   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.
@@ -28,8 +23,9 @@ 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;