Implement <appview> based on out-of-process iframes GuestView.

extensions/renderer/dispatcher.cc

Index: extensions/renderer/dispatcher.cc
diff --git a/extensions/renderer/dispatcher.cc b/extensions/renderer/dispatcher.cc
index a31eda7eea84987adc2f49c007c735cd924f7ef7..df828dcc4856a49e5c627612b396d2fcf7f4df75 100644
--- a/extensions/renderer/dispatcher.cc
+++ b/extensions/renderer/dispatcher.cc
@@ -1582,6 +1582,8 @@ void Dispatcher::RequireGuestViewModules(ScriptContext* context) {
   // Require AppView.
   if (context->GetAvailability("appViewEmbedderInternal").is_available()) {
     module_system->Require("appView");
+
+    guest_view_required = true;
   }
 
   // Require ExtensionOptions.