predictors: Use redirect data in prefetch.

chrome/browser/predictors/resource_prefetch_predictor_tables.cc

 // Copyright 2014 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.
 
 #include "chrome/browser/predictors/resource_prefetch_predictor_tables.h"
 
 #include <stdint.h>
 
 #include <algorithm>
 #include <memory>
@@ skipping 356 matching lines @@
 
   constexpr int kMaxResourcesPerType = 100;
   return kMaxResourcesPerType *
              (priority_multiplier * 100 + type_multiplier * 10) -
          data.average_position();
 }
 
 // static
 float ResourcePrefetchPredictorTables::ComputeRedirectScore(
     const RedirectStat& data) {
-  // TODO(alexilin): Invent some scoring.
-  return 0.0;
+  return (data.number_of_hits() + 0.0) /
+         (data.number_of_hits() + data.number_of_misses());

[pasko, 2016/10/07 11:42:43]

If this is not covered by any tests, it would be nice to create once: populate
redirect tables, read back the redirects and check for their order.

[alexilin, 2016/10/07 13:09:29]

I've just realized that we don't have to sort redirects because we need only the
best one for populating prefetch. It could be done by single pass through the
array instead of (potentially) n*log(n) sorting.
So I removed this code.

 }
 
 // static
 bool ResourcePrefetchPredictorTables::DropTablesIfOutdated(
     sql::Connection* db) {
   int version = GetDatabaseVersion(db);
   bool success = true;
   // Too new is also a problem.
   bool incompatible_version = version != kDatabaseVersion;
 
@@ skipping 128 matching lines @@
       return is_host ? kHostResourceTableName : kUrlResourceTableName;
     case PrefetchDataType::REDIRECT:
       return is_host ? kHostRedirectTableName : kUrlRedirectTableName;
   }
 
   NOTREACHED();
   return nullptr;
 }
 
 }  // namespace predictors