Improve performance relative to native implementation

[webcomponents]

Improve performance relative to native implementation

[bicknellr]

@sorvell, closable?

[dalvarezmartinez1]

We're having similar problems for big datasets, loading a datatable with ~7000 rows and 4 columns takes about 5min with the custom-elements polyfill (IE11), and around 5 seconds without (Chrome67).

After looking at the performance tab I discovered that most of the time (~99%) is spent adding or removing children (depending on the usecase: initial load or reload), the 3rd column (98.36%) is percentage of the whole time of those 5 minutes.

I would attach the .diagsession which can be loaded into Edge, but it's ~ 80MB which is bigger than the 10MB limit.

[dfreedm]

Not sure if you still need help with this @dalvarezmartinez1, but you should use https://github.com/webcomponents/polyfills/tree/master/packages/custom-elements#customelementspolyfillwrapflushcallback