Summary:
This makes a few changes to React Core, most notably `ReactEventEmitter` and `ReactEventTopLevelCallback`.
- Changed `ReactEventEmitter` to use `EventListener` (instead of `NormalizedEventListener`).
- Deleted `NormalizedEventListener` (which was previously broken).
- Created `getEventTarget` which is used to get a normalized `target` from a native event.
- Changed `ReactEventTopLevelCallback` to use `getEventTarget`.
- Renamed `abstractEventType` to `reactEventType` in `AbstractEvent`.
- Reanmed `abstractTargetID` to `reactTargetID` in `AbstractEvent`.
- Removed `originatingTopLevelEventType` from `AbstractEvent` (unused and violates encapsulation).
- Removed `nativeEvent.target === window` check when refreshing authoritative scroll values (unnecessary).
This actually fixes React because `NormalizedEventListener` does not currently do what it promises to do (which is normalizing `target` on the native event). The `target` event is read-only on native events.
This also revises documentation and adds `@typechecks` to a few modules.
NOTE: Most importantly, this sets the stage for replacing `AbstractEvent` with `ReactEvent` and subclasses, piecemeal.
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Paul O’Shannessy