This problem is introduced by Electron 1.6.x, it's the same issue as microsoft/monaco-editor#320, but we didn't fix all the problems via eb08a8d but that fix targets v55 but Electron 1.6.x ships with Chrome v56.

We need to

1. Check Chrome version, both v55 and v56 are wrong about composition update
2. When we receive compositionUpdate event, textarea doesn't get updated yet so the value of the texarea is obsolete. We need to postpone the specialized composition update for Chrome v55/56 to onInput event.

cc @bpasero @alexandrudima