Analyze, debug, and improve the performance of your Lightning application (Developer Preview)
The Salesforce Page Optimizer (Developer Preview) analyzes your lightning based community/apps and identifies performance optimization opportunites. Use the information to refine your design and improve performance for your members.
Installation and usage of this extension is covered by the EULA: https://secure2.sfdcstatic.com/assets/pdf/misc/salesforce-community-eula-ofs-page-optimizer.pdf
Check out the Settings > Privacy page for more information on what data is gathered/used by this extension.