Webview: no longer emits onfocus event

[bpasero]

• Electron Version: 3.0.0-beta.6
• Operating System (Platform and Version): macOS
• Last known working Electron version: 3.0.0-beta.5

Expected Behavior
The onfocus event is fired when clicking into a webview contents.

Actual behavior
The onfocus event is not fired.

To Reproduce

• run this fiddle: https://gist.github.com/bpasero/eb6f5e94b463883d5445a96ab9a0b1ba
• click into the input box of the GitHub landing page
• observe that the onfocus event is not emitted

This breaks VSCode's focus tracking when the user clicks into a webview.

[ckerr]

Running in fiddle, I'm seeing the same behavior as described as @bpasero -- this works in 2.0.x and up through 3.0.0-beta.5, then is broken in beta.6 and beta.7

[zcbenz]

Hmm in old architecture the webview is a browser plugin which is an actually DOM element that can get focus, but with OOPIF the webview is an iframe, and there is no real way to listen to the focus/blur events of an iframe.

I'll see if I can find a way to hack this.