Prevent creating background pages for non-incognito profile in Guest mode

extensions/browser/extensions_browser_client.h

Index: extensions/browser/extensions_browser_client.h
diff --git a/extensions/browser/extensions_browser_client.h b/extensions/browser/extensions_browser_client.h
index 71b0ea602a504afaaf70acf452c142552f4965d4..c93b629995a3519022aef34292b88b4592aa69d3 100644
--- a/extensions/browser/extensions_browser_client.h
+++ b/extensions/browser/extensions_browser_client.h
@@ -68,6 +68,9 @@ class ExtensionsBrowserClient {
   virtual bool DeferLoadingBackgroundHosts(
       content::BrowserContext* context) const = 0;
 
+  virtual bool IsBackgroundPageAllowed(
+      content::BrowserContext* context) const = 0;
+
   // Returns true if the client version has updated since the last run. Called
   // once each time the extensions system is loaded per browser_context. The
   // implementation may wish to use the BrowserContext to record the current