Help: Implement the initial version of the cross-platform help/about page.

chrome/browser/ui/webui/help/version_updater.h

Index: chrome/browser/ui/webui/help/version_updater.h
diff --git a/chrome/browser/ui/webui/help/version_updater.h b/chrome/browser/ui/webui/help/version_updater.h
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+// Copyright (c) 2012 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 CHROME_BROWSER_UI_WEBUI_HELP_VERSION_UPDATER_H_
+#define CHROME_BROWSER_UI_WEBUI_HELP_VERSION_UPDATER_H_
+#pragma once
+
+#include "base/callback.h"
+
+// Interface implemented to expose per-platform updating functionality.
+class VersionUpdater {
+ public:
+  // Update process state machine.
+  enum Status {
+    CHECKING,
+    UPDATING,
+    NEARLY_UPDATED,
+    UPDATED
+  };
+
+  // Used to update the client of status changes. int parameter is the progress
+  // and should only be non-zero for the UPDATING state.
+  typedef base::Callback<void(Status, int)> StatusCallback;
+
+  virtual ~VersionUpdater() {}
+
+  // Sub-classes must implement this method to create the respective
+  // specialization.
+  static VersionUpdater* Create();
+
+  // Begins the update process.  |callback| is called for each status update.
+  virtual void CheckForUpdate(const StatusCallback& callback) = 0;
+
+  // Relaunches the browser, generally after being updated.
+  virtual void RelaunchBrowser() const = 0;
+};
+
+#endif  // CHROME_BROWSER_UI_WEBUI_HELP_VERSION_UPDATER_H_