Save pipelining capabilities for the most used hosts between sessions.

base/memory/mru_cache.h

 // Copyright (c) 2011 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.
 
 // This file contains a template for a Most Recently Used cache that allows
 // constant-time access to items using a key, but easy identification of the
 // least-recently-used items for removal.  Each key can only be associated with
 // one payload item at a time.
 //
 // The key object will be stored twice, so it should support efficient copying.
@@ skipping 132 matching lines @@
 
   // MRUCache entries are often processed in reverse order, so we add this
   // convenience function (not typically defined by STL containers).
   reverse_iterator Erase(reverse_iterator pos) {
     // We have to actually give it the incremented iterator to delete, since
     // the forward iterator that base() returns is actually one past the item
     // being iterated over.
     return reverse_iterator(Erase((++pos).base()));
   }
 
+  // Updates the |max_size_| of the cache to |new_max_size| and evicts entries,
+  // if necessary, to satisfy the new maximum.
+  void SetMaxSize(size_t new_max_size) {

[mmenke, 2011/12/06 15:50:38]

You're going to need a signoff from an owner of base to land this CL.  Even
without this added function, you still have the const iterator fixes.

[James Simonsen, 2011/12/06 19:57:49]

Yeah, Will's an owner and he's already given LGTM for the const changes.

+    if (new_max_size < max_size_) {
+      ShrinkToSize(new_max_size);
+    }
+    max_size_ = new_max_size;
+  }
+
   // Shrinks the cache so it only holds |new_size| items. If |new_size| is
   // bigger or equal to the current number of items, this will do nothing.
   void ShrinkToSize(size_type new_size) {
     for (size_type i = size(); i > new_size; i--)
       Erase(rbegin());
   }
 
   // Deletes everything from the cache.
   void Clear() {
     for (typename PayloadList::iterator i(ordering_.begin());
@@ skipping 11 matching lines @@
     return index_.size();
   }
 
   // Allows iteration over the list. Forward iteration starts with the most
   // recent item and works backwards.
   //
   // Note that since these iterators are actually iterators over a list, you
   // can keep them as you insert or delete things (as long as you don't delete
   // the one you are pointing to) and they will still be valid.
   iterator begin() { return ordering_.begin(); }
-  const_iterator begin() const { ordering_.begin(); }
+  const_iterator begin() const { return ordering_.begin(); }
   iterator end() { return ordering_.end(); }
   const_iterator end() const { return ordering_.end(); }
 
   reverse_iterator rbegin() { return ordering_.rbegin(); }
-  const_reverse_iterator rbegin() const { ordering_.rbegin(); }
+  const_reverse_iterator rbegin() const { return ordering_.rbegin(); }
   reverse_iterator rend() { return ordering_.rend(); }
   const_reverse_iterator rend() const { return ordering_.rend(); }
 
   bool empty() const { return ordering_.empty(); }
 
  private:
   PayloadList ordering_;
   KeyIndex index_;
 
   size_type max_size_;
@@ skipping 97 matching lines @@
   virtual ~HashingMRUCache() {
   }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(HashingMRUCache);
 };
 
 }  // namespace base
 
 #endif  // BASE_MEMORY_MRU_CACHE_H_