precache: Add geometric resource weight function.

components/precache/core/precache_fetcher.h

 // 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.
 
 #ifndef COMPONENTS_PRECACHE_CORE_PRECACHE_FETCHER_H_
 #define COMPONENTS_PRECACHE_CORE_PRECACHE_FETCHER_H_
 
 #include <stdint.h>
 
 #include <deque>
 #include <list>
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "base/single_thread_task_runner.h"
 #include "base/time/time.h"
 #include "components/precache/core/fetcher_pool.h"
+#include "components/precache/core/proto/precache.pb.h"
 #include "components/precache/core/proto/quota.pb.h"
 #include "net/url_request/url_fetcher.h"
 #include "net/url_request/url_fetcher_delegate.h"
 #include "url/gurl.h"
 
 namespace base {
 class SingleThreadTaskRunner;
 }
 
 namespace net {
@@ skipping 230 matching lines @@
 
   // Daily quota.
   PrecacheQuota quota_;
 
   // The fieldtrial experiment ID.
   uint32_t experiment_id_;
 
   DISALLOW_COPY_AND_ASSIGN(PrecacheFetcher);
 };
 
+// Visible for testing.
+double ResourceWeight(
+    PrecacheConfigurationSettings::ResourceWeightFunction function,
+    double resource_weight_ratio,
+    int64_t host_visits);
+
 // Class that fetches a URL, and runs the specified callback when the fetch is
 // complete. This class exists so that a different method can be run in
 // response to different kinds of fetches, e.g. OnConfigFetchComplete when
 // configuration settings are fetched, OnManifestFetchComplete when a manifest
 // is fetched, etc.
 //
 // This class tries to increase freshness while limiting network usage, by using
 // the following strategy:
 // 1.  Fetch the URL from the cache.
 // 2a. If it's present and lacks revalidation headers, then stop.
@@ skipping 53 matching lines @@
   int64_t response_bytes_;
   int64_t network_response_bytes_;
   bool was_cached_;
 
   DISALLOW_COPY_AND_ASSIGN(Fetcher);
 };
 
 }  // namespace precache
 
 #endif  // COMPONENTS_PRECACHE_CORE_PRECACHE_FETCHER_H_