This patch defines mozilla::SelectionType as an enum class. This is safer than nsISelectionController::SELECTION_* since setting illegal value to its variable is checked at build time. So, as far as possible, this should be used everywhere (but of course, this isn't available in scriptable interfaces).
And also this implements some useful methods for managing SelectionType and RawSelectionType which are implemented in layout/nsSelection.cpp because nsISelectionController is implemented by both PresShell and nsTextEditorState. Therefore, implementing one of them may make hard to find them. On the other hand, nsSelection.cpp is a better file name to look for them.
Note that this patch creates mozilla::Selection::RawType() for binding. Native code should keep using Selection::Type() but the binding code needs to use RawType() due to impossible to convert from SelectionType to RawSelectionType without explicit cast.
MozReview-Commit-ID: 81vX7A0hHQN
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extra : rebase_source : d9f88e217c713c60d1c2578ce6421c73ccba8650