### 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:** 10.1.3
* **Operating System:** Windows 10
* **Last Known Working Electron version:** 10.1.2

### Expected Behavior
I expect that a BrowserView that's set up to auto resize, will do so

### Actual Behavior
No auto-resizing happens

### To Reproduce
1. start the app below
2. when the page loads in the browserview, resize the window
3. notice the black background. browser view doesn't resize

main.js:
```
const { app, BrowserWindow, BrowserView } = require('electron')

async function createWindow() {
  const mainWindow = new BrowserWindow({ backgroundColor: "#000" });
  const view = new BrowserView();
  mainWindow.setBrowserView(view);

  const contentBounds = mainWindow.getContentBounds();
  view.setBounds({ x: 0, y: 0, width: contentBounds.width, height: contentBounds.height });
  view.setAutoResize({ width: true, height: true });

  await view.webContents.loadURL("https://google.com");
}

app.on('ready', createWindow)
```
shell/browser/native_browser_view_views.cc
auto new_view_size = view->size();
    new_view_size.set_width(new_view_size.width() + width_delta);
    new_view_size.set_height(new_view_size.height() + height_delta);
    view->SetSize(new_view_size);
  }
  auto new_view_bounds = view->bounds();
  if (flags & kAutoResizeHorizontal) {
    new_view_bounds.set_width(new_window.width() /
                              auto_horizontal_proportion_width_);
    new_view_bounds.set_x(new_window.width() /
                          auto_horizontal_proportion_left_);
  }
  if (flags & kAutoResizeVertical) {
    new_view_bounds.set_height(new_window.height() /
                               auto_vertical_proportion_height_);
    new_view_bounds.set_y(new_window.height() / auto_vertical_proportion_top_);
  }
  if ((flags & kAutoResizeHorizontal) || (flags & kAutoResizeVertical)) {
    view->SetBoundsRect(new_view_bounds);
  }
}
void NativeBrowserViewViews::ResetAutoResizeProportions() {
  if (auto_resize_flags_ & AutoResizeFlags::kAutoResizeHorizontal) {
    auto_horizontal_proportion_set_ = false;
  }
  if (auto_resize_flags_ & AutoResizeFlags::kAutoResizeVertical) {
    auto_vertical_proportion_set_ = false;
  }
}
void NativeBrowserViewViews::SetBounds(const gfx::Rect& bounds) {