### 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
gin_helper::Promise<gin_helper::Dictionary> promise(isolate);
  v8::Local<v8::Promise> handle = promise.GetHandle();
  auto* frame_host = ontents()->GetMainFrame();
  if (!frame_host) {
    promise.RejectWithErrorMessage("Failed to create memory dump");
    return handle;
  }
  auto pid = frame_host->GetProcess()->GetProcess().Pid();
  v8::Global<v8::Context> context(isolate, isolate->GetCurrentContext());
  memory_instrumentation::MemoryInstrumentation::GetInstance()
      ->RequestGlobalDumpForPid(
          pid, std::vector<std::string>(),
          base::BindOnce(&ElectronBindings::DidReceiveMemoryDump,
                         std::move(context), std::move(promise), pid));
  return handle;
}
v8::Local<v8::Promise> WebContents::TakeHeapSnapshot(
    v8::Isolate* isolate,
    const base::FilePath& file_path) {
  gin_helper::Promise<void> promise(isolate);
  v8::Local<v8::Promise> handle = promise.GetHandle();
  base::ThreadRestrictions::ScopedAllowIO allow_io;
  base::File file(file_path,
                  base::File::FLAG_CREATE_ALWAYS | base::File::FLAG_WRITE);
  if (!file.IsValid()) {
    promise.RejectWithErrorMessage("takeHeapSnapshot failed");
    return handle;
  }
  auto* frame_host = ontents()->GetMainFrame();
  if (!frame_host) {