PerformanceEntry object encapsulates a single performance metric that is part of the performance timeline. A performance entry can be directly created by making a performance
measure (for example by calling the
mark() method) at an explicit point in an application. Performance entries are also created in indirect ways such as loading a resource (such as an image).
PerformanceEntry instances will always be one of the following subtypes:
Note: This feature is available in Web Workers