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* Electron version: 1.7.11
* Operating system: win10 x64

i want record every frame to make a video,

### Expected behavior

stop painting page, until call startPainting()

### Actual behavior

not stop painting page

### How to reproduce
```js
const electron = require('electron');
const fs = require('fs');
const app = electron.app
const BrowserWindow = electron.BrowserWindow

let mainWindow

// app.disableHardwareAcceleration()
function createWindow() {
  mainWindow = new BrowserWindow({
    width: 480, height: 800, frame: false, resizable: false, // show: false,
    webPreferences: {
      offscreen: true
    }
  })
  // mainWindow = new BrowserWindow({ width: 480, height: 800 })
  var i = 0;
  mainWindow.webContents.on('paint', (event, dirty, image) => {
    mainWindow.webContents.stopPainting()
    const data = image.toPNG()
    fs.writeFileSync('./f/' + i++ + '.png', data)
    // mainWindow.webContents.startPainting()
  })
  mainWindow.webContents.setFrameRate(1)

  mainWindow.on('closed', function () {
    mainWindow = null
  })
  
  var url = 'https://github.com';
  mainWindow.loadURL(url)
  //mainWindow.webContents.openDevTools()

}

app.on('ready', createWindow)
app.on('window-all-closed', function () {
  if (process.platform !== 'darwin') {
    app.quit()
  }
})
app.on('activate', function () {
  if (mainWindow === null) {
    createWindow()
  }
})
```

atom/browser/api/atom_api_web_contents.cc
.SetMethod("isLoading", &WebContents::IsLoading)
      .SetMethod("isLoadingMainFrame", &WebContents::IsLoadingMainFrame)
      .SetMethod("isWaitingForResponse", &WebContents::IsWaitingForResponse)
      .SetMethod("_stop", &WebContents::Stop)
      .SetMethod("_goBack", &WebContents::GoBack)
      .SetMethod("_goForward", &WebContents::GoForward)
      .SetMethod("_goToOffset", &WebContents::GoToOffset)
      .SetMethod("isCrashed", &WebContents::IsCrashed)
      .SetMethod("setUserAgent", &WebContents::SetUserAgent)
      .SetMethod("getUserAgent", &WebContents::GetUserAgent)
      .SetMethod("savePage", &WebContents::SavePage)
      .SetMethod("openDevTools", &WebContents::OpenDevTools)
      .SetMethod("closeDevTools", &WebContents::CloseDevTools)
      .SetMethod("isDevToolsOpened", &WebContents::IsDevToolsOpened)
      .SetMethod("isDevToolsFocused", &WebContents::IsDevToolsFocused)
      .SetMethod("enableDeviceEmulation", &WebContents::EnableDeviceEmulation)
      .SetMethod("disableDeviceEmulation", &WebContents::DisableDeviceEmulation)
      .SetMethod("toggleDevTools", &WebContents::ToggleDevTools)
      .SetMethod("inspectElement", &WebContents::InspectElement)
      .SetMethod("setIgnoreMenuShortcuts",
                 &WebContents::SetIgnoreMenuShortcuts)
      .SetMethod("setAudioMuted", &WebContents::SetAudioMuted)
      .SetMethod("isAudioMuted", &WebContents::IsAudioMuted)
      .SetMethod("undo", &WebContents::Undo)
      .SetMethod("redo", &WebContents::Redo)
      .SetMethod("cut", &WebContents::Cut)
      .SetMethod("copy", &WebContents::Copy)
      .SetMethod("paste", &WebContents::Paste)
      .SetMethod("pasteAndMatchStyle", &WebContents::PasteAndMatchStyle)
      .SetMethod("delete", &WebContents::Delete)