Convert mouse-related events to use InputCoder.
Convert serialization of HandleKeyPress to use InputCoder.
Convert wheel input serialization to use InputCoder. Update Timelapse's special PlatformWheelEvent constructor to include more mac-only initializers.
Convert NavigateToPage to use InputCoder. Add InputCoder<T>::decode template with RefPtr out-parameter, since OwnPtr and RefPtr are unconvertible.
Convert RanPendingScripts, ScrollPage, SendResizeEvent to use InputCoder.