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Ref #19447

### Issue Details

* **Electron Version:**
  * 9.0.0-beta.24
* **Operating System:**
  * macOS 10.15, Windows 10
* **Last Known Working Electron version:**
  * none

### Expected Behavior
`e.sender` object received from an extension background page should have `webPreferences` and `session` initialized. It looks like `options` in `api::WebContents` constructor don't get initialized properly for an extension background page.

### Actual Behavior
`e.sender` object doesn't have `session` and `e.sender.getWebPreferences()` returns `null`.

### To Reproduce
https://github.com/sentialx/electron-quick-start/tree/extensions/no-session

Just run it and you will see something like this:
![image](https://user-images.githubusercontent.com/11065386/82097607-82994400-9703-11ea-8291-0eb987d8aca0.png)

### Additional Information
This is a real blocker for anyone who would want to provide own `chrome` APIs in background pages initialized from different sessions.
shell/browser/api/electron_api_web_contents.cc
auto* osr_wcv = GetOffScreenWsView();
  return osr_wcv ? osr_wcv->GetFrameRate() : 0;
}
#endif
void Ws::Invalidate() {
  if (IsOffScreen()) {
#if BUILDFLAG(ENABLE_OSR)
    auto* osr_rwhv = GetOffScreenRenderWidgetHostView();
    if (osr_rwhv)
      osr_rwhv->Invalidate();
#endif
  } else {
    auto* const window = owner_window();
    if (window)
      window->Invalidate();
  }
}
gfx::Size Ws::GetSizeForNewRenderView(content::Ws* wc) {
  if (IsOffScreen() && wc == ontents()) {
    auto* relay = NativeWindowRelay::FromWs(ontents());
    if (relay) {
      auto* owner_window = relay->GetNativeWindow();
      return owner_window ? owner_window->GetSize() : gfx::Size();
    }
  }
  return gfx::Size();
}
void Ws::SetZoomLevel(double level) {