Electron: investigate to use `requestSingleInstanceLock()` API

[bpasero]

Currently VSCode is implementing it's own solution for preventing a second instance from starting. Electron provides API to do the same but there are differences: https://github.com/electron/electron/blob/7-1-x/docs/api/app.md#apprequestsingleinstancelock

Things we need:

• pass the process environment over (second-instance event should pass ENV of requester electron/electron#18434)
• communicate between second and first instance to support code --status [1]

[1] code --status will print information about the active window in the first instance to the console of the second instance and thus requires access to the workspace, including remote scenarios.

[rzhao271]

Electron's requestSingleInstanceLock() API is a wrapper on top of Chromium. In other words, the implementation heavily depends on what Chromium is doing.

The general shape of the callback is determined at process_singleton.h: https://source.chromium.org/chromium/chromium/src/+/main:chrome/browser/process_singleton.h;l=102

The Chromium implementation is process-dependent. The following links are for the Windows implementation:

The part that transfers the commandLine and workingDirectory information from one instance to another is at AttemptToNotifyRunningChrome: https://source.chromium.org/chromium/chromium/src/+/main:chrome/browser/win/chrome_process_finder.cc;l=37;drc=477e08a0f1fc11af8e1147dda5edb86b74f04e64

The callback that takes in those same commandLine and workingDirectory args is run during ProcessLaunchNotification: https://source.chromium.org/chromium/chromium/src/+/main:chrome/browser/process_singleton_win.cc;l=172

Bonus: I was getting confused by what all the bind functions were doing. It's explained well at https://source.chromium.org/chromium/chromium/src/+/main:base/bind.h

[rzhao271]

Update: Electron has a copy of those files here: https://github.com/electron/electron/tree/main/chromium_src/chrome/browser

Removing chromium label.

[deepak1556]

Adding relevant upstream issues,

pass the process environment over

electron/electron#18434
electron/electron#23220

communicate between second and first instance to support code --status

electron/electron#20942