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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
base::ScopedBlockingCall scoped_blocking_call(FROM_HERE,
                                                base::BlockingType::MAY_BLOCK);
  scoped_refptr<printing::PrintBackend> backend =
      printing::PrintBackend::CreateInstance(
          nullptr, g_browser_process->GetApplicationLocale());
  std::string printer_name = backend->GetDefaultPrinterName();
  return base::UTF8ToUTF16(printer_name);
}
#endif
e
Ws::Ws(v8::Isolate* isolate,
                         content::Ws* ontents)
    : content::WsObserver(ontents),
      type_(Type::REMOTE),
      weak_factory_(this) {
  ontents->SetUserAgentOverride(blink::UserAgentOverride::UserAgentOnly(
                                         GetBrowserContext()->GetUserAgent()),
                                     false);
  Init(isolate);
  AttachAsUserData(ontents);
  InitZoomController(ontents, gin::Dictionary::CreateEmpty(isolate));
#if BUILDFLAG(ENABLE_ELECTRON_EXTENSIONS)
  extensions::ElectronExtensionWsObserver::CreateForWs(
      ontents);
  script_executor_.reset(new extensions::ScriptExecutor(ontents));
#endif
  registry_.AddInterface(base::BindRepeating(&Ws::BindElectronBrowser,
                                             base::Unretained(this)));
  bindings_.set_connection_error_handler(base::BindRepeating(
      &Ws::OnElectronBrowserConnectionError, base::Unretained(this)));