Reland: Refactor and shorten in-memory cache.

net/disk_cache/memory/mem_rankings.cc

-// Copyright (c) 2006-2008 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 "net/disk_cache/memory/mem_rankings.h"
-
-#include "base/logging.h"
-#include "net/disk_cache/memory/mem_entry_impl.h"
-
-namespace disk_cache {
-
-MemRankings::~MemRankings() {
-  DCHECK(!head_ && !tail_);
-}
-
-void MemRankings::Insert(MemEntryImpl* node) {
-  if (head_)
-    head_->set_prev(node);
-
-  if (!tail_)
-    tail_ = node;
-
-  node->set_prev(NULL);
-  node->set_next(head_);
-  head_ = node;
-}
-
-void MemRankings::Remove(MemEntryImpl* node) {
-  MemEntryImpl* prev = node->prev();
-  MemEntryImpl* next = node->next();
-
-  if (head_ == node)
-    head_ = next;
-
-  if (tail_ == node)
-    tail_ = prev;
-
-  if (prev)
-    prev->set_next(next);
-
-  if (next)
-    next->set_prev(prev);
-
-  node->set_next(NULL);
-  node->set_prev(NULL);
-}
-
-void MemRankings::UpdateRank(MemEntryImpl* node) {
-  Remove(node);
-  Insert(node);
-}
-
-MemEntryImpl* MemRankings::GetNext(MemEntryImpl* node) {
-  if (!node)
-    return head_;
-
-  return node->next();
-}
-
-MemEntryImpl* MemRankings::GetPrev(MemEntryImpl* node) {
-  if (!node)
-    return tail_;
-
-  return node->prev();
-}
-
-}  // namespace disk_cache