One "undo" cancels several typed letters or lines in Mac version

[chiehan1]

In Mac version 0.1.50, if not typing very slowly, one "undo" won't only cancel one letter, it may cancel several letters or lines once.

[kmsheng]

@chiehan1 History event delay can be adjusted if this is the issue. http://codemirror.net/3/doc/manual.html

historyEventDelay: integer
The period of inactivity (in milliseconds) that will cause a new history event to be started
 when typing or deleting. Defaults to 500.

[kmsheng]