### Preflight Checklist

- [X] I have read the [Contributing Guidelines](https://github.com/electron/electron/blob/main/CONTRIBUTING.md) for this project.
- [X] I agree to follow the [Code of Conduct](https://github.com/electron/electron/blob/main/CODE_OF_CONDUCT.md) that this project adheres to.
- [X] I have searched the [issue tracker](https://www.github.com/electron/electron/issues) for a feature request that matches the one I want to file, without success.

### Electron Version

16.0.0

### What operating system are you using?

macOS

### Operating System Version

macOS Monterey 12.0.1

### What arch are you using?

x64

### Last Known Working Electron version

n/a

### Expected Behavior

Window does not have a white background when vibrancy is set to under-window + transparent background is used on macOS

### Actual Behavior

Window with vibrancy and transparency enabled is rendered with a white background, at random

### Testcase Gist URL

_No response_

### Additional Information

We're still hitting random issues with Electron where creating a window with vibrancy + transparent body will result in a white background. I was hopeful that the 16.0.0 release would have fixed this as it was mentioned in the changelog, but seems like the issue persists.

I've tried to narrow down to a reproducible case, but didn't manage to do so - I've observed all these variations across executions:

- Window opens with correct vibrancy effect, and it works without issues
- Windows opens with correct vibrancy effect then goes white after ~4 seconds - consistently after ~4 seconds
- Window opens with correct vibrancy, stays without issues, but loses after some time of switching between apps
- Windows open with effect already not working and a white background

I've already tried all suggestions from previous issues like #30993 or #31461 . The window is created with vibrancy set to under-window, has a transparent background and the webpreferences also has a transparent background set. As it works sometimes, I assume the options here are correct.

My guess is that this is somehow related to #31019: Electron is using somehow the background color of the HTML body. As we initially load the window with about:empty, then navigate to our url, the transparent background logic might be loading the incorrect background color at random times and breaking the transparency/vibrancy effect from there on. 

I also don't know if #31722 is already merged on the 16.0.0 release - happy to test if not the case once it is again!

shell/browser/api/electron_api_web_contents.cc
.SetMethod("setIgnoreMenuShortcuts", &WebContents::SetIgnoreMenuShortcuts)
      .SetMethod("setAudioMuted", &WebContents::SetAudioMuted)
      .SetMethod("isAudioMuted", &WebContents::IsAudioMuted)
      .SetMethod("isCurrentlyAudible", &WebContents::IsCurrentlyAudible)
      .SetMethod("undo", &WebContents::Undo)
      .SetMethod("redo", &WebContents::Redo)
      .SetMethod("cut", &WebContents::Cut)
      .SetMethod("copy", &WebContents::Copy)
      .SetMethod("paste", &WebContents::Paste)
      .SetMethod("pasteAndMatchStyle", &WebContents::PasteAndMatchStyle)
      .SetMethod("delete", &WebContents::Delete)
      .SetMethod("selectAll", &WebContents::SelectAll)
      .SetMethod("unselect", &WebContents::Unselect)
      .SetMethod("replace", &WebContents::Replace)
      .SetMethod("replaceMisspelling", &WebContents::ReplaceMisspelling)
      .SetMethod("findInPage", &WebContents::FindInPage)
      .SetMethod("stopFindInPage", &WebContents::StopFindInPage)
      .SetMethod("focus", &WebContents::Focus)
      .SetMethod("isFocused", &WebContents::IsFocused)
      .SetMethod("sendInputEvent", &WebContents::SendInputEvent)
      .SetMethod("beginFrameSubscription", &WebContents::BeginFrameSubscription)
      .SetMethod("endFrameSubscription", &WebContents::EndFrameSubscription)
      .SetMethod("startDrag", &WebContents::StartDrag)
      .SetMethod("attachToIframe", &WebContents::AttachToIframe)
      .SetMethod("detachFromOuterFrame", &WebContents::DetachFromOuterFrame)
      .SetMethod("isOffscreen", &WebContents::IsOffScreen)
#if BUILDFLAG(ENABLE_OSR)
      .SetMethod("startPainting", &WebContents::StartPainting)
      .SetMethod("stopPainting", &WebContents::StopPainting)
      .SetMethod("isPainting", &WebContents::IsPainting)