### Preflight Checklist
<!-- Please ensure you've completed the following steps by replacing [ ] with [x]-->

* [x] I have read the [Contributing Guidelines](https://github.com/electron/electron/blob/master/CONTRIBUTING.md) for this project.
* [x] I agree to follow the [Code of Conduct](https://github.com/electron/electron/blob/master/CODE_OF_CONDUCT.md) that this project adheres to.
* [x] I have searched the issue tracker for an issue that matches the one I want to file, without success.

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
#include "shell/common/gin_converters/image_converter.h"
#include "shell/common/gin_converters/net_converter.h"
#include "shell/common/gin_converters/value_converter.h"
#include "shell/common/gin_helper/dictionary.h"
#include "shell/common/gin_helper/object_template_builder.h"
#include "shell/common/language_util.h"
#include "shell/common/mouse_util.h"
#include "shell/common/node_includes.h"
#include "shell/common/options_switches.h"
#include "shell/common/v8_value_serializer.h"
#include "third_party/blink/public/common/associated_interfaces/associated_interface_provider.h"
#include "third_party/blink/public/common/input/web_input_event.h"
#include "third_party/blink/public/common/messaging/transferable_message_mojom_traits.h"
#include "third_party/blink/public/common/page/page_zoom.h"
#include "third_party/blink/public/mojom/frame/find_in_page.mojom.h"
#include "third_party/blink/public/mojom/frame/fullscreen.mojom.h"
#include "third_party/blink/public/mojom/messaging/transferable_message.mojom.h"
#include "third_party/blink/public/mojom/renderer_preferences.mojom.h"
#include "ui/base/cursor/cursor.h"
#include "ui/base/cursor/mojom/cursor_type.mojom-shared.h"
#include "ui/display/screen.h"
#include "ui/events/base_event_utils.h"
#if BUILDFLAG(ENABLE_OSR)
#include "shell/browser/osr/osr_render_widget_host_view.h"
#include "shell/browser/osr/osr_ontents_view.h"
#endif
#if !defined(OS_MACOSX)
#include "ui/aura/window.h"
#else
#include "ui/base/cocoa/defaults_utils.h"