Change InMemoryContentStore to use MRUCache.

components/dom_distiller/core/distilled_content_store.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 "components/dom_distiller/core/distilled_content_store.h"
 
 #include "base/message_loop/message_loop.h"
 
 namespace dom_distiller {
 
-InMemoryContentStore::InMemoryContentStore() {}
-InMemoryContentStore::~InMemoryContentStore() {}
+InMemoryContentStore::InMemoryContentStore(const int max_num_entries)
+    : cache_(max_num_entries) {
+}
+
+InMemoryContentStore::~InMemoryContentStore() {
+}
 
 void InMemoryContentStore::SaveContent(
     const ArticleEntry& entry,
     const DistilledArticleProto& proto,
     InMemoryContentStore::SaveCallback callback) {
   InjectContent(entry, proto);
   if (!callback.is_null()) {
     base::MessageLoop::current()->PostTask(FROM_HERE,
                                            base::Bind(callback, true));
   }
 }
 
 void InMemoryContentStore::LoadContent(
     const ArticleEntry& entry,
-    InMemoryContentStore::LoadCallback callback) const {
+    InMemoryContentStore::LoadCallback callback) {
   if (callback.is_null())
     return;
 
-  ContentMap::const_iterator it = cache_.find(entry.entry_id());
+  ContentMap::const_iterator it = cache_.Get(entry.entry_id());
   bool success = it != cache_.end();
   scoped_ptr<DistilledArticleProto> distilled_article;
   if (success) {
     distilled_article.reset(new DistilledArticleProto(it->second));
   } else {
     distilled_article.reset(new DistilledArticleProto());
   }
   base::MessageLoop::current()->PostTask(
       FROM_HERE,
       base::Bind(callback, success, base::Passed(&distilled_article)));
 }
 
 void InMemoryContentStore::InjectContent(const ArticleEntry& entry,
                                          const DistilledArticleProto& proto) {
-  cache_[entry.entry_id()] = proto;
+  cache_.Put(entry.entry_id(), proto);
 }
 
 }  // namespace dom_distiller