Webview post messages are not posted to the notebook controller

[colombod]

Version: 1.56.0-insider (user setup)
Commit: 23a2409
Date: 2021-04-21T05:13:42.491Z
Electron: 12.0.4
Chrome: 89.0.4389.114
Node.js: 14.16.0
V8: 8.9.255.24-electron.0
OS: Windows_NT x64 10.0.19042

Steps to Reproduce:

1. Clone pr update to new apis dotnet/interactive#1286
2. Go to folder src/dotnet-interactive-vscode/nsiders adn open with VSCode insiders
3. Launch debugger
4. set breakpoint in src/dotnet-interactive-vscode/insiders/src/notebookControllers.ts at line 89
5. Open a .dib or .ipynb notebook

The breakpoint is never hit despite the preloads are posting the messages (the developer tools for the web view will show it in console)

Does this issue occur when all extensions are disabled?: Yes/No

[vscodebot]

(Experimental duplicate detection)
Thanks for submitting this issue. Please also check if it is already covered by an existing one, like:

• Terminal Split not working (#121880)

[colombod]

cc: @brettfo, @jrieken

[jrieken]

postMessage should be fixed with 306f32b

[jrieken]

related/dupe (?) of #121869

[colombod]

Perfect, when can we test this fix?

[jrieken]

Should be in latest insiders

[colombod]

Perfect!