Polymer/ShadowDOM — pull request #505 by jmesserly (2014-09-09 21:12:44+00:00)
Title: fixes #504, avoids global list of all MutationObservers

They're now added to the global list on-demand, and it is sorted by ID before delivering. Sounds like this is similar to the Blink implementation https://github.com/Polymer/ShadowDOM/issues/504#issuecomment-55013158