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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
const gfx::Rect& rect) {
  for (ExtendedWsObserver& observer : observers_)
    observer.OnSetContentBounds(rect);
}
void Ws::CloseContents(content::Ws* source) {
  Emit("close");
  auto* autofill_driver_factory =
      AutofillDriverFactory::FromWs(ontents());
  if (autofill_driver_factory) {
    autofill_driver_factory->CloseAllPopups();
  }
  if (managed_ontents())
    managed_ontents()->GetView()->SetDelegate(nullptr);
  for (ExtendedWsObserver& observer : observers_)
    observer.OnCloseContents();
}
void Ws::ActivateContents(content::Ws* source) {
  for (ExtendedWsObserver& observer : observers_)
    observer.OnActivateContents();
}
void Ws::UpdateTargetURL(content::Ws* source,