React's top-level event delegation dispatches `AbstractEvent` objects that contain:
- `nativeEvent`, the original browser event.
- `data`, an object with custom normalized properties.
This diff creates a set of `DelegateEvent` classes that will replace `AbstractEvent`. The goal is two-fold:
# Provide a cross-browser implementation that conforms to the DOM Level 3 Events API so people don't have to use `nativeEvent`.
# Generalize the event object API so that it can be shared by `DOMEventManager`, a top-level event delegation WIP.
This simply implements the classes. I will follow-up by replacing `AbstractEvent` with them.
CommitSyncScript
Paul O’Shannessy