WebUI NTP: fix logo shrinking when it is larger than min-height

Bug: 1091367
Change-Id: I8283c28f0bdbb2b1fa87bdab76e2dc508ff6bdb3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2231291
Commit-Queue: Esmael Elmoslimany <aee@chromium.org>
Commit-Queue: Tibor Goldschwendt <tiborg@chromium.org>
Auto-Submit: Esmael Elmoslimany <aee@chromium.org>
Reviewed-by: Tibor Goldschwendt <tiborg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#775241}

chrome/browser/resources/new_tab_page/logo.html

@@ -2,6 +2,7 @@
   :host {
     --ntp-logo-height: 230px;
     display: inline-block;
+    flex-shrink: 0;
     min-height: var(--ntp-logo-height);
   }