scanning: Set minimum window size of the Scan app

To align with the spec, set the Scan app's minimum width to 600px and
its minimum height to 420px.

Bug: 1059779
Change-Id: Ibdcb95f47533748c4be2b57892edfab7c61aaed3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2568070
Auto-Submit: Jesse Schettler <jschettler@chromium.org>
Commit-Queue: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Reviewed-by: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Cr-Commit-Position: refs/heads/master@{#832654}

chrome/browser/web_applications/system_web_app_manager.cc

@@ -203,6 +203,7 @@ base::flat_map<SystemAppType, SystemAppInfo> CreateSystemWebApps(
                   SystemAppInfo("Scanning", GURL("chrome://scanning"),
                                 base::BindRepeating(
                                     &CreateWebAppInfoForScanningSystemWebApp)));
+    infos.at(SystemAppType::SCANNING).minimum_window_size = {600, 420};
   }
 
   if (SystemWebAppManager::IsAppEnabled(