predictors: Refactor resource_prefetch_predictor_tables.

chrome/browser/predictors/resource_prefetch_predictor.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.
 
 // Protocol buffers used for storing in SQLite.
 // CAUTION: When any change is done here, bump kDatabaseVersion in
 //          resource_prefetch_predictor_tables.h.
 
 syntax = "proto2";
 
 package predictors;
 
 // Required in Chrome.
 option optimize_for = LITE_RUNTIME;
 
-message Metadata {
-  optional string main_page_url = 1;
-  optional uint64 last_visit_time = 2;
-}
-
+// Represents a single subresource.
 message ResourceData {
   // Mirrors content::ResourceType.
   enum ResourceType {
     RESOURCE_TYPE_MAIN_FRAME = 0;
     RESOURCE_TYPE_SUB_FRAME = 1;
     RESOURCE_TYPE_STYLESHEET = 2;
     RESOURCE_TYPE_SCRIPT = 3;
     RESOURCE_TYPE_IMAGE = 4;
     RESOURCE_TYPE_FONT_RESOURCE = 5;
     RESOURCE_TYPE_SUB_RESOURCE = 6;
@@ skipping 24 matching lines @@
   optional ResourceType resource_type = 2;
   optional uint32 number_of_hits = 3;
   optional uint32 number_of_misses = 4;
   optional uint32 consecutive_misses = 5;
   optional double average_position = 6;
   optional Priority priority = 7;
   optional bool has_validators = 8;
   optional bool always_revalidate = 9;
 }
 
+// Represents a collection of subresources associated with URL or host.
+message PrefetchData {
+  // Main frame URL of host.
+  optional string primary_key = 1;
+  optional uint64 last_visit_time = 2;
+  repeated ResourceData resources = 3;
+}
+
 // Represents a mapping from URL or host to a list of redirect endpoints.
 message RedirectData {
   // Represents a single redirect chain endpoint.
   message RedirectStat {
     // Represents the host for RedirectData in a host-based table.
     optional string url = 1;
     optional uint32 number_of_hits = 2;
     optional uint32 number_of_misses = 3;
     optional uint32 consecutive_misses = 4;
   }
 
-  // Represents main frame URL or host.
+  // Main frame URL or host.
   optional string primary_key = 1;
   optional uint64 last_visit_time = 2;
   repeated RedirectStat redirect_endpoints = 3;
 }