Add a DistilledContentStore (and an in-memory impl)

components/dom_distiller/core/distilled_content_store.h

+// 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.
+
+#ifndef COMPONENTS_DOM_DISTILLER_CORE_DOM_DISTILLER_CONTENT_STORE_H_
+#define COMPONENTS_DOM_DISTILLER_CORE_DOM_DISTILLER_CONTENT_STORE_H_
+
+#include "base/bind.h"
+#include "base/containers/hash_tables.h"
+#include "components/dom_distiller/core/article_entry.h"
+#include "components/dom_distiller/core/proto/distilled_article.pb.h"
+
+namespace dom_distiller {
+
+// This is a simple interface for saving and loading of distilled content for an
+// ArticleEntry.
+class DistilledContentStore {
+ public:
+  typedef base::Callback<
+      void(bool /* success */, scoped_ptr<DistilledArticleProto>)> LoadCallback;
+  typedef base::Callback<void(bool /* success */)> SaveCallback;
+
+  virtual void SaveContent(const ArticleEntry& entry,
+                           const DistilledArticleProto& proto,
+                           SaveCallback callback) = 0;
+  virtual void LoadContent(const ArticleEntry& entry,
+                           LoadCallback callback) const = 0;
+
+  DistilledContentStore() {};
+  virtual ~DistilledContentStore() {};
+ private:
+  DISALLOW_COPY_AND_ASSIGN(DistilledContentStore);
+};
+
+class InMemoryContentStore : public DistilledContentStore {

[nyquist, 2014/04/14 22:42:22]

This is very simple and nice for now. But this store can have unbounded growth
with no support for cleaning up. Could you add a quick comment explaining that?
I guess it is kind of given with the name *Store instead of *Cache, but still,
it would be nice to clarify.

+ public:
+  InMemoryContentStore();
+  virtual ~InMemoryContentStore();
+
+  // DistilledContentStore implementation
+  virtual void SaveContent(const ArticleEntry& entry,
+                           const DistilledArticleProto& proto,
+                           SaveCallback callback) OVERRIDE;
+  virtual void LoadContent(const ArticleEntry& entry,
+                           LoadCallback callback) const OVERRIDE;
+
+  // Synchronously saves the content.
+  void InjectContent(const ArticleEntry& entry,
+                     const DistilledArticleProto& proto);
+
+ private:
+  typedef base::hash_map<std::string, DistilledArticleProto> ContentMap;
+  ContentMap cache_;
+};
+}  // dom_distiller
+
+#endif  // COMPONENTS_DOM_DISTILLER_CORE_DOM_DISTILLER_CONTENT_CACHE_H_