Refactors DeviceOrientation to make it more extensible

content/browser/device_orientation/device_data.h

Index: content/browser/device_orientation/device_data.h
diff --git a/content/browser/device_orientation/device_data.h b/content/browser/device_orientation/device_data.h
new file mode 100644
index 0000000000000000000000000000000000000000..29039aad6b6dfde2b56c4a3e7ced427bf7fc6077
--- /dev/null
+++ b/content/browser/device_orientation/device_data.h
@@ -0,0 +1,30 @@
+// 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 "ipc/ipc_message.h"

[hans, 2012/07/18 17:21:02]

i guess this is for IPC::Message?
You could just forward-declare it like this:

namespace IPC {
class Message;
}

[aousterh, 2012/07/20 11:18:52]

Done.

+
+namespace device_orientation {
+
+class DeviceData {

[hans, 2012/07/18 17:21:02]

Should this class be RefCounted? (RefCountedThreadSafe if we're accessing it
from different threads) Now that we're going to be passing around pointers to
DeviceData where we were previously passing and storing Orientation objects by
value, the ownership situation seems to become a bit unclear..

[aousterh, 2012/07/20 11:18:52]

Done.

+ public:
+  enum Type {
+    kTypeOrientation
+  };
+  virtual ~DeviceData() {}
+
+  virtual DeviceData* Clone() const = 0;

[hans, 2012/07/18 17:21:02]

if we make it ref counted, we might not need to Clone() it..

[aousterh, 2012/07/20 11:18:52]

Done.

+  virtual bool IsEmpty() const = 0;
+  virtual bool SignificantlyDifferentFrom(const DeviceData& other) const = 0;
+  virtual IPC::Message* CreateIPCMessage(int render_view_id) const = 0;
+
+  static bool IsElementSignificantlyDifferent(bool can_provide_element1,

[hans, 2012/07/18 17:21:02]

hmm, we might actually want to implement the notion of being significantly
different differently for different types of data. Maybe keep this in the
derived class for now.

[aousterh, 2012/07/20 11:18:52]

ok, i moved IsElementSignificantlyDifferent to the derived class (Orientation),
and replaced SignificantlyDifferentFrom with ShouldFireEvent in the base class,
to determine from the old device data whether an event should be fired. I think
the name is slightly confusing though - it's not clear why the function is
called on one DeviceData with another as an argument, so if you have any
suggestions, please let me know!

+      bool can_provide_element2, double element1, double element2);
+};
+
+}  // namespace device_orientation
+
+#endif  // CONTENT_BROWSER_DEVICE_ORIENTATION_DEVICE_DATA_H_