Use PreloadCheckGroup in ExtensionInstallChecker. Make RequirementsChecker a PreloadCheck.

extensions/browser/api/management/management_api_delegate.h

Index: extensions/browser/api/management/management_api_delegate.h
diff --git a/extensions/browser/api/management/management_api_delegate.h b/extensions/browser/api/management/management_api_delegate.h
index b2219073e82d625072f41dc6e8092ee331920548..ebb953ce18e025d89abd6450d515b3bf31292358 100644
--- a/extensions/browser/api/management/management_api_delegate.h
+++ b/extensions/browser/api/management/management_api_delegate.h
@@ -83,10 +83,6 @@ class ManagementAPIDelegate {
       const Extension* extension,
       const base::Callback<void(bool)>& callback) const = 0;
 
-  // Returns a new RequirementsChecker.
-  virtual std::unique_ptr<RequirementsChecker> CreateRequirementsChecker()
-      const = 0;
-
   // Enables the extension identified by |extension_id|.
   virtual void EnableExtension(content::BrowserContext* context,
                                const std::string& extension_id) const = 0;