predictors: Add Manifest table to ResourcePrefetchPredictor.

components/precache/core/proto/precache.proto

 // Copyright 2013 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";
 
 package precache;
 
 // Chrome requires this.
 option optimize_for = LITE_RUNTIME;
@@ skipping 15 matching lines @@
   // This is a non-negative number, with higher being more important. Its value
   // depends on PrecacheConfigurationSettings.resource_weight_function.
   optional double weight = 4;
 };
 
 message PrecacheManifestId {
   optional int64 id = 1;
 };
 
 // A manifest of cacheable resources to be precached for a specific host.
+// CAUTION: When any change is done here, bump kDatabaseVersion in
+// chrome/browser/predictors/resource_prefetch_predictor_tables.h
 message PrecacheManifest {
   // List of resources that we predict that the user will need if they are
   // likely to fetch the host.
   repeated PrecacheResource resource = 1;
 
   // Experiments running on this manifest.
   optional PrecacheExperiments experiments = 2;
 
   // Identifier for the manifest sent by the server.
   optional PrecacheManifestId id = 3;
@@ skipping 89 matching lines @@
     // days, given that weight_ratio is a probability that a visit to the host
     // will request a resource, and host_visits is an estimate of the number of
     // visits to the host in the next 30 days.
     FUNCTION_NAIVE = 0;
     // Models the probability of at least one request, given the same.
     FUNCTION_GEOMETRIC = 1;
   };
   optional ResourceWeightFunction resource_weight_function = 11
       [default = FUNCTION_NAIVE];
 };