Add a HostContentSettingsMap layer for Supervised Users.

chrome/test/base/testing_profile.cc

Index: chrome/test/base/testing_profile.cc
diff --git a/chrome/test/base/testing_profile.cc b/chrome/test/base/testing_profile.cc
index 75d2c5ca8736137cc198e0598aa7709594136293..32792a18ebadc498ba3daee4316887230f4bc0fc 100644
--- a/chrome/test/base/testing_profile.cc
+++ b/chrome/test/base/testing_profile.cc
@@ -909,6 +909,12 @@ HostContentSettingsMap* TestingProfile::GetHostContentSettingsMap() {
           host_content_settings_map_.get());
     }
 #endif
+#if defined(ENABLE_SUPERVISED_USERS)
+    SupervisedUserSettingsService* supervised_service =
+        SupervisedUserSettingsServiceFactory::GetForProfile(this);
+    supervised_service->RegisterContentSettings(
+        host_content_settings_map_.get());
+#endif
   }
   return host_content_settings_map_.get();
 }