[Offline] Adding archiver interface

components/offline_pages/offline_page_archiver.h

+// Copyright 2015 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_OFFLINE_PAGE_ARCHIVER_H_
+#define COMPONENTS_OFFLINE_PAGES_OFFLINE_PAGE_ARCHIVER_H_
+
+#include "base/files/file_path.h"
+#include "url/gurl.h"
+
+namespace offline_pages {
+
+// Interface of a class responsible for creation of the archive for offline use.
+class OfflinePageArchiver {
+ public:
+  // Represents an in progress request to archive a page.
+  class Request {
+   public:
+    virtual ~Request();
+
+    // Cancels an in progress request to archive a page.
+    virtual void Cancel() = 0;
+    virtual const GURL& url() const = 0;
+  };
+
+  // Errors that will be reported when archive creation fails.
+  enum ArchiveError {
+    ERROR_UNKNOWN,              // Don't know what went wrong.
+    ERROR_DEVICE_FULL,          // Cannot save the archive - device is full.
+    ERROR_CANCELLED,            // Caller cancelled the request.
+    ERROR_CONTENT_UNAVAILABLE,  // Content to archive is not available.
+  };
+
+  // Interface of the clients that requests to archive pages.
+  class Client {
+   public:
+    virtual ~Client();
+
+    // Callback called by the archiver upon successful creation of the archive.
+    virtual void OnCreateArchiveSuccess(Request* request,
+                                        const base::FilePath& file_path) = 0;
+    // Callback called by the archiver when it fails to create the archive.
+    virtual void OnCreateArchiveFailure(Request* request,
+                                        ArchiveError error) = 0;
+  };
+
+  virtual ~OfflinePageArchiver();
+
+  // Starts creating the archive. Will pass result by calling methods on the
+  // passed in client. Caller owns the returned request object.
+  // If request is deleted during the archiving, the callback will not be
+  // invoked. The archive might however be created.
+  virtual scoped_ptr<Request> CreateArchive(const GURL& url,
+                                            Client* client) = 0;
+};
+
+}  // namespace offline_pages
+
+#endif  // COMPONENTS_OFFLINE_PAGES_OFFLINE_PAGE_ARCHIVER_H_