droppedEntriesCount in PerformanceObserverCallback

[npm1]

Request for Mozilla Position on an Emerging Web Specification

• This request is only for the small addition of the hasDroppedEntry parameter to PerformanceObserverCallback, which is in https://w3c.github.io/performance-timeline/#the-performanceobserver-interface, and logic for it in https://w3c.github.io/performance-timeline/#queue-the-performanceobserver-task. It lets a developer know when an entry has been dropped from a buffer that the PerformanceObserver cares about.
• Caniuse.com URL (optional): this is relevant to PerformanceObserver so https://caniuse.com/#feat=mdn-api_performanceobserver is relevant.
• Mozillians who can provide input (optional): this was discussed in WebPerf WG so perhaps @bdekoz can provide input.

[annevk]

cc @Bas-moz

[sefeng211]

This issue should be repurposed to droppedEntriesCount as hasDroppedEntry no longer exists. In addition to that, there are some conversations about changing it further in https://github.com/w3c/performance-timeline/issues/181.