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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
blink::WebMouseWheelEvent mouse_wheel_event;
    if (gin::ConvertFromV8(isolate, input_event, &mouse_wheel_event)) {
      if (IsOffScreen()) {
#if BUILDFLAG(ENABLE_OSR)
        GetOffScreenRenderWidgetHostView()->SendMouseWheelEvent(
            mouse_wheel_event);
#endif
      } else {
         Chromium expects phase info in wheel events (and applies a
         DCHECK to verify it). See: https:crbug.com/756524.
        mouse_wheel_event.phase = blink::WebMouseWheelEvent::kPhaseBegan;
        mouse_wheel_event.dispatch_type =
            blink::WebInputEvent::DispatchType::kBlocking;
        rwh->ForwardWheelEvent(mouse_wheel_event);
         Send a synthetic wheel event with phaseEnded to finish scrolling.
        mouse_wheel_event.has_synthetic_phase = true;
        mouse_wheel_event.delta_x = 0;
        mouse_wheel_event.delta_y = 0;
        mouse_wheel_event.phase = blink::WebMouseWheelEvent::kPhaseEnded;
        mouse_wheel_event.dispatch_type =
            blink::WebInputEvent::DispatchType::kEventNonBlocking;
        rwh->ForwardWheelEvent(mouse_wheel_event);
      }
      return;
    }
  }
  isolate->ThrowException(
      v8::Exception::Error(gin::StringToV8(isolate, "Invalid event object")));
}
void Ws::BeginFrameSubscription(gin_helper::Arguments* args) {