Defines initial inner circle of interfaces for background offlining.

components/offline_pages/background/offliner.h

+// Copyright 2016 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_OFFLINE_PAGES_BACKGROUND_OFFLINER_H_
+#define COMPONENTS_OFFLINE_PAGES_BACKGROUND_OFFLINER_H_
+
+#include "base/callback.h"
+
+namespace offline_pages {
+
+class SavePageRequest;
+
+// Interface of a class responsible for constructing an offline page given
+// a request with a URL.
+class Offliner {
+ public:
+  // Completion status of processing an offline page request.
+  enum CompletionStatus {
+    SAVED = 0,
+    CANCELED = 1,
+    FAILED_CONSIDER_RETRY = 2,
+    FAILED_DO_NOT_RETRY = 3,
+  };
+
+  // Reports the completion status of a request.
+  // TODO(dougarnett): consider passing back a request id instead of request.
+  typedef base::Callback<void(const SavePageRequest& request, CompletionStatus)>

[dewittj, 2016/04/26 18:28:00]

I think that technically a forward declaration of SavePageRequest is
insufficient to make this header compile, since you're using a const ref.

[dougarnett, 2016/04/26 18:45:59]

replaced with struct for this CL/iteration

+      CompletionCallback;
+
+  Offliner() {}
+  virtual ~Offliner() {}
+
+  // Processes |request| to load and save an offline page.
+  // Returns whether the request was accepted or not.
+  virtual bool LoadAndSave(
+      const SavePageRequest& request,
+      const CompletionCallback& callback) = 0;
+
+  // Clears the currently processing request, if any.
+  virtual void Cancel() = 0;
+
+  // TODO(dougarnett): add policy support methods.
+};
+
+}  // namespace offline_pages
+
+#endif  // COMPONENTS_OFFLINE_PAGES_BACKGROUND_OFFLINER_H_