Browser viewport size becomes 14x14 when form minimized

### Is there an existing issue for this?

- [x] I have searched both open/closed issues, no issue already exists.

### CefSharp Version

138.0.170

### Operating System

Windows 11

### Architecture

x64

### .Net Version

.Net 4.7.2

### Implementation

WinForms

### Reproduction Steps

1. Open URL https://www.part987.com/en/standard/
2. Wait for website loading finished - it should look like normal desktop website
3. Minimize window

### Expected behavior

Website should remains unchanged

### Actual behavior

Website immediately changes to mobile version

### Regression?

_No response_

### Known Workarounds

This website tracks viewport size and redirects to mobile version as soon as width becomes small enough (about 400px and less). This is how we can check that viewport size has changed. I guess it becomes 1x1 or 0x0, but I can't confirm that.
It happens on window minimize, not on restore.

### Does this problem also occur in the CEF Sample Application

No

### Other information

Cefclient - works fine
CefSharp minimal application - problem exists

Start by reproducing the issue in the CefSharp minimal WinForms application and compare its minimize behavior with the CEF sample application and cefclient. Trace how the WinForms browser integration handles window minimization and viewport updates; done means minimizing the form no longer changes the website to its mobile layout while the restored viewport remains correct.

Written by the indexing model from the issue text.