Bad window resize performance in electron 9.0.0

Preflight Checklist

• I have read the Contributing Guidelines for this project.
• I agree to follow the Code of Conduct that this project adheres to.
• I have searched the issue tracker for an issue that matches the one I want to file, without success.

Issue Details

• Electron Version:
  • 9.0.0
• Operating System:
  • macOS 10.14.6
• Last Known Working Electron version:
  • 8.x

Expected Behavior

Resizing a window is smooth

Actual Behavior

Resizing a window is unexpectedly laggy, even when the window is completely empty and there are no other active listeners

To Reproduce

The following simple program exhibits the poor behavior:

$ electron index.js

// index.js
const BrowserWindow = require("electron").BrowserWindow;
const app = require("electron").app;

app.on("ready", () => {
  new BrowserWindow();
})

Screenshots

Additional Information

Notes:

• To the best of my knowledge, this worked well in previous versions of Electron
• Interestingly, at super tiny sizes, like making the window 80px x 60px, resizing works just fine. The resizing performance degrades significantly starting at about 600 x 400.

Thanks much for such an awesome technology. Let me know if there’s anything I can do to help diagnose potential confounding issues here!