predictors: Add resource type to manifest.

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;
 
 // Information about a cacheable resource to be precached.
 message PrecacheResource {
   // The URL of the resource. This field must always be present.
   optional string url = 1;
 
   // The tophost this resource corresponds to.
   optional string top_host_name = 2;
 
   // How important this resource is for the host. It ranges from 0.0 to 1.0.
   // Higher values mean more important.
   optional double weight_ratio = 3;
 
   // How important this resource is for the client; a combination of
   // weight_ratio and TopHost.visits. Populated only in PrecacheUnfinishedWork.
   // This is a non-negative number, with higher being more important. Its value
   // depends on PrecacheConfigurationSettings.resource_weight_function.
   optional double weight = 4;
+
+  enum Type {
+    RESOURCE_TYPE_UNKNOWN = 0;
+
+    RESOURCE_TYPE_IMAGE = 1;
+    RESOURCE_TYPE_FONT = 2;
+    RESOURCE_TYPE_STYLESHEET = 3;
+    RESOURCE_TYPE_SCRIPT = 4;
+
+    RESOURCE_TYPE_OTHER = 7;
+  }
+
+  // The type of resource.
+  optional Type type = 5;

[Benoit L, 2017/04/27 08:54:15]

Does the precache code need to be updated in any way?

[alexilin, 2017/04/27 15:32:23]

I don't think so. This field was in real manifests for a while as unknown_field
and declaring it explicitly in .proto shouldn't change anything. 

 };
 
 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 {
@@ skipping 98 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];
 };