[Reland][Extensions] Enable sideloading prompt on mac on canary

chrome/browser/extensions/extension_service.cc

Index: chrome/browser/extensions/extension_service.cc
diff --git a/chrome/browser/extensions/extension_service.cc b/chrome/browser/extensions/extension_service.cc
index f63d065691ddbbcf599e44a68daec2e58506328c..748fb3e5ded1599ea1da1ef12b6647c5fb88e90a 100644
--- a/chrome/browser/extensions/extension_service.cc
+++ b/chrome/browser/extensions/extension_service.cc
@@ -2258,7 +2258,7 @@ int ExtensionService::GetDisableReasonsOnInstalled(const Extension* extension) {
                : disable_reasons;
   }
 
-  if (FeatureSwitch::prompt_for_external_extensions()->IsEnabled()) {
+  if (extensions::ExternalInstallManager::IsPromptingEnabled()) {
     // External extensions are initially disabled. We prompt the user before
     // enabling them. Hosted apps are excepted because they are not dangerous
     // (they need to be launched by the user anyway). We also don't prompt for