Demo UI made with a help of WUG toolkit (DO NOT SEND TO CQ).

chrome/chrome_browser_ui.gypi

Index: chrome/chrome_browser_ui.gypi
diff --git a/chrome/chrome_browser_ui.gypi b/chrome/chrome_browser_ui.gypi
index 5bb7f3a3ee002f142050b05b095e396b9318d1bd..9219b7561a6d146624e60d011d4b5d95aef0b87b 100644
--- a/chrome/chrome_browser_ui.gypi
+++ b/chrome/chrome_browser_ui.gypi
@@ -1032,6 +1032,16 @@
       'browser/ui/webui/crashes_ui.h',
       'browser/ui/webui/device_log_ui.cc',
       'browser/ui/webui/device_log_ui.h',
+      'browser/ui/webui/demo_ui/demo.cc',
+      'browser/ui/webui/demo_ui/demo.h',
+      'browser/ui/webui/demo_ui/demo_ui.cc',
+      'browser/ui/webui/demo_ui/demo_ui.h',
+      'browser/ui/webui/demo_ui/events/events_demo.cc',
+      'browser/ui/webui/demo_ui/events/events_demo.h',
+      'browser/ui/webui/demo_ui/strings/strings_demo.cc',
+      'browser/ui/webui/demo_ui/strings/strings_demo.h',
+      'browser/ui/webui/demo_ui/reuse/reuse_demo.cc',
+      'browser/ui/webui/demo_ui/reuse/reuse_demo.h',
       'browser/ui/webui/domain_reliability_internals_ui.cc',
       'browser/ui/webui/domain_reliability_internals_ui.h',
       'browser/ui/webui/favicon_source.cc',
@@ -2730,6 +2740,11 @@
             '../components/components.gyp:app_modal',
             '../components/components.gyp:autofill_content_risk_proto',
             '../components/components.gyp:translate_content_common',
+            '../components/components.gyp:demo_wug_generated',
+            '../components/components.gyp:events_demo_wug_generated',
+            '../components/components.gyp:reuse_demo_wug_generated',
+            '../components/components.gyp:strings_demo_wug_generated',
+            '../components/components.gyp:webui_generator',
             '../content/app/resources/content_resources.gyp:content_resources',
             '../media/media.gyp:media',
             '../net/net.gyp:net_with_v8',