### Preflight Checklist
* [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.

### Issue Details

* **Electron Version:**
  * 9.0.0-beta.2
  * 8.0.1
  * 7.1.13
  * 7.0.0
* **Operating System:**
  * `Linux xps 5.5.4-arch1-1 #1 SMP PREEMPT Sat, 15 Feb 2020 00:36:29 +0000 x86_64 GNU/Linux` (Arch Linux current)
  * macOS 10.15.3
* **Last Known Working Electron version:**
  * 6.1.8 -- fine, not affected

### Expected Behavior
* When `safeDialogs` option is used, I expect to see a "Prevent this app from creating additional dialogs" checkbox on all alerts after the first one, like it happened in Electron 6.1.8.
* I expect `safeDialogs` option to do at least something.

Basically, how 6.x behaves.

### Actual Behavior
* That checkbox does not appear on second alert, or on any other subsequent alert (tried about 10).
* There seems to no observable difference at all between turning that option on or off.

### To Reproduce

```js
const { BrowserWindow, app } = require('electron')
app.on('ready', () => {
  const window = new BrowserWindow({
    webPreferences: {
      //partition: 'memory',
      safeDialogs: true,
    }
  })
  window.webContents.loadURL('about:blank') // also could be e.g. https://example.com/
  window.webContents.on('did-finish-load', () => {
    window.webContents.executeJavaScript(`
      document.body.innerText = window.navigator.userAgent // (not required)
      alert(0)
      setTimeout(() => { alert(1) }, 100) // timeout for UA to be shown
    `)
  })
  window.show()
})
```

### Screenshots
#### v6.1.8 (correct behavior)
![Screenshot_20200223_221526](https://user-images.githubusercontent.com/291301/75118279-dad32380-5689-11ea-84bd-fbb93d3fefb2.png)

#### v7.0.0
![Screenshot_20200223_222330](https://user-images.githubusercontent.com/291301/75118399-e410c000-568a-11ea-8b3b-e414cb0b8c6b.png)

#### v7.1.13
![Screenshot_20200223_221938](https://user-images.githubusercontent.com/291301/75118348-5f25a680-568a-11ea-8a18-7fb253ea90e6.png)

#### v8.0.1
![Screenshot_20200223_222409](https://user-images.githubusercontent.com/291301/75118421-115d6e00-568b-11ea-9d1e-30dc4201fb17.png)

#### 9.0.0-beta.2
![Screenshot_20200223_222754](https://user-images.githubusercontent.com/291301/75118467-7ca74000-568b-11ea-830f-2cfe2a11ba73.png)

###

### Additional Information
* Documented here: https://www.electronjs.org/docs/api/browser-window#new-browserwindowoptions
* This does not seem to be a duplicate of closed #17543, as this affects only versions starting from v7.0.0.
* This does not seem to be a problem of specific configuration/url/scheme/whatever -- I was not able to make that option work on a recent Electron version with any attempted configuration.

shell/browser/electron_javascript_dialog_manager.cc
#include "shell/browser/electron_javascript_dialog_manager.h"
#include <string>
#include <utility>
#include <vector>
#include "base/bind.h"
#include "base/strings/utf_string_conversions.h"
#include "shell/browser/api/electron_api_web_contents.h"
#include "shell/browser/native_window.h"
#include "shell/browser/ui/message_box.h"
#include "shell/browser/web_contents_preferences.h"
#include "shell/common/options_switches.h"
#include "ui/gfx/image/image_skia.h"
using content::JavaScriptDialogType;
namespace electron {
namespace {
constexpr int kUserWantsNoMoreDialogs = -1;
}  
ElectronJavaScriptDialogManager::ElectronJavaScriptDialogManager(