Remove Reflect Metadata polyfill for core-js

[coryrylan]

It looks like es7 reflect metadata is now in core-js. The CLI & Material are removing the separate package in favor of using core-js. The live examples and demos will need to be updated as well.

angular/angular-cli#853
angular/components#505

[Foxandxss]

We are aware of that, but we haven't made a decision yet.

I'll put it on my list of things to discuss.

/cc @filipesilva

[filipesilva]

Let's talk about it early next week.

[kylecordes]

core-js appears to do the whole job, and work very well. The advantage of fewer dependencies seems transparently obvious. So I will be very interested to see (and I hope a rationale is published) if the decision is made to keep the extra reflect-metadata.

[schmuli]

What about updating angular/core too?

https://github.com/angular/angular/blob/master/modules/%40angular/core/src/util/decorators.ts#L266

[filipesilva]

@schmuli core-js includes reflect-metadata, and more. Angular itself just requires that reflect-metadata is present.

[schmuli]

My confusion was because there is the reflect-metadata NPM package, so I thought it was referring to the package, not the feature.