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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
if (debugger_.IsEmpty()) {
    auto handle = electron::api::Debugger::Create(isolate, ontents());
    debugger_.Reset(isolate, handle.ToV8());
  }
  return v8::Local<v8::Value>::New(isolate, debugger_);
}
void Ws::GrantOriginAccess(const GURL& url) {
  content::ChildProcessSecurityPolicy::GetInstance()->GrantCommitOrigin(
      ontents()->GetMainFrame()->GetProcess()->GetID(),
      url::Origin::Create(url));
}
void Ws::NotifyUserActivation() {
  auto* frame = ontents()->GetMainFrame();
  if (!frame)
    return;
  mojo::AssociatedRemote<mojom::ElectronRenderer> renderer;
  frame->GetRemoteAssociatedInterfaces()->GetInterface(&renderer);
  renderer->NotifyUserActivation();
}
v8::Local<v8::Promise> Ws::TakeHeapSnapshot(
    const base::FilePath& file_path) {
  gin_helper::Promise<void> promise(isolate());
  v8::Local<v8::Promise> handle = promise.GetHandle();
  base::ThreadRestrictions::ScopedAllowIO allow_io;
  base::File file(file_path,
                  base::File::FLAG_CREATE_ALWAYS | base::File::FLAG_WRITE);
  if (!file.IsValid()) {