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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
static
void Ws::BuildPrototype(v8::Isolate* isolate,
                                 v8::Local<v8::FunctionTemplate> prototype) {
  prototype->SetClassName(gin::StringToV8(isolate, "Ws"));
  gin_helper::Destroyable::MakeDestroyable(isolate, prototype);
  gin_helper::ObjectTemplateBuilder(isolate, prototype->PrototypeTemplate())
      .SetMethod("getBackgroundThrottling",
                 &Ws::GetBackgroundThrottling)
      .SetMethod("setBackgroundThrottling",
                 &Ws::SetBackgroundThrottling)
      .SetMethod("getProcessId", &Ws::GetProcessID)
      .SetMethod("getOSProcessId", &Ws::GetOSProcessID)
      .SetMethod("_getOSProcessIdForFrame",
                 &Ws::GetOSProcessIdForFrame)
      .SetMethod("equal", &Ws::Equal)
      .SetMethod("_loadURL", &Ws::LoadURL)
      .SetMethod("downloadURL", &Ws::DownloadURL)
      .SetMethod("_getURL", &Ws::GetURL)
      .SetMethod("getTitle", &Ws::GetTitle)
      .SetMethod("isLoading", &Ws::IsLoading)
      .SetMethod("isLoadingMainFrame", &Ws::IsLoadingMainFrame)
      .SetMethod("isWaitingForResponse", &Ws::IsWaitingForResponse)
      .SetMethod("_stop", &Ws::Stop)
      .SetMethod("_goBack", &Ws::GoBack)
      .SetMethod("_goForward", &Ws::GoForward)
      .SetMethod("_goToOffset", &Ws::GoToOffset)
      .SetMethod("isCrashed", &Ws::IsCrashed)
      .SetMethod("setUserAgent", &Ws::SetUserAgent)
      .SetMethod("getUserAgent", &Ws::GetUserAgent)
      .SetMethod("savePage", &Ws::SavePage)