Switch guest profile from forced-incognito to UI mods like ChromeOS.

chrome/browser/extensions/chrome_extensions_browser_client.cc

Index: chrome/browser/extensions/chrome_extensions_browser_client.cc
diff --git a/chrome/browser/extensions/chrome_extensions_browser_client.cc b/chrome/browser/extensions/chrome_extensions_browser_client.cc
index 728407488db70bf41405a12b9a294ae613744408..23d2e255c385c9a5eb0efd925ec96b02cbf40870 100644
--- a/chrome/browser/extensions/chrome_extensions_browser_client.cc
+++ b/chrome/browser/extensions/chrome_extensions_browser_client.cc
@@ -120,17 +120,11 @@ bool ChromeExtensionsBrowserClient::DeferLoadingBackgroundHosts(
 
 bool ChromeExtensionsBrowserClient::IsBackgroundPageAllowed(
     content::BrowserContext* context) const {
-#if defined(OS_CHROMEOS)
-  // Returns true if current session is Chrome OS Guest mode session and current
+  // Returns true if current session is Guest mode session and current
   // browser context is *not* off-the-record. Such context is artificial and
   // background page shouldn't be created in it.
-  const CommandLine* command_line = CommandLine::ForCurrentProcess();
-  if (command_line->HasSwitch(chromeos::switches::kGuestSession) &&
-      !context->IsOffTheRecord()) {
-    return false;
-  }
-#endif
-  return true;
+  return !static_cast<Profile*>(context)->IsGuestSession() ||
+         context->IsOffTheRecord();
 }
 
 void ChromeExtensionsBrowserClient::OnExtensionHostCreated(