Refactors DeviceOrientation to make it more extensible

content/browser/device_orientation/device_data.h

+// 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 CONTENT_BROWSER_DEVICE_ORIENTATION_DEVICE_DATA_H_
+#define CONTENT_BROWSER_DEVICE_ORIENTATION_DEVICE_DATA_H_
+
+#include "base/memory/ref_counted.h"
+
+namespace IPC {
+class Message;
+}
+
+namespace device_orientation {
+
+class DeviceData : public base::RefCountedThreadSafe<DeviceData> {
+ public:
+  enum Type {
+    kTypeOrientation
+  };
+
+  virtual IPC::Message* CreateIPCMessage(int render_view_id) const = 0;
+  virtual bool ShouldFireEvent(const DeviceData* other) const = 0;
+
+ protected:
+  DeviceData() {}

[hans, 2012/07/30 16:12:52]

i'm not sure this constructor is necessary?

[aousterh, 2012/08/03 11:08:14]

I believe it is necessary because any constructor in a derived class needs to
call a constructor of the base class. 

If I remove it, I get the compiler error "constructor for
'device_orientation::Orientation' must explicitly initialize the base class
'device_orientation::DeviceData' which does not have a default constructor'.

+  virtual ~DeviceData() {}
+
+ private:
+  friend class base::RefCountedThreadSafe<DeviceData>;
+
+  DISALLOW_COPY_AND_ASSIGN(DeviceData);
+};
+
+}  // namespace device_orientation
+
+#endif  // CONTENT_BROWSER_DEVICE_ORIENTATION_DEVICE_DATA_H_