Add Math property to Window

[zuzusik]

Fixes microsoft/TypeScript#9325

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[mhegazy]

As noted in microsoft/TypeScript#9325 (comment), i do not see why we need to define this but not other ones, e.g. NaN, Array, Date, Number, String, HTMLElement, etc..

[saschanaz]

From microsoft/TypeScript#9325 (comment):

The standard library does not support using Window as the global polluter. i.e. adding members on Window are not reflected on the global and adding members on the global are not reflected on Window.

Not sure what this means, can you elaborate more? I thought JSON, Math, RegExp, etc are all accessible via window and delete window.RegExp makes the global member inaccessible.

[zuzusik]

@mhegazy then I suppose you should also delete Blob and URL from window?

In general this sounds strange to me. If these props exist on window, why shouldn't it be described in TypeScript definitions?

[saschanaz]

@zuzusik Web specifications explicitly say Exposed=Window in their WebIDL but JS standard libraries do not. However, not really understand TypeScript policy yet...

[mhegazy]

This file is autogrenerated mostly, so we shown ones marked as such. i am fine adding more to window but do not see why add Math, but nothing else.

[mhegazy]

As i have noted earlier, do not see why Math is any different from other declarations. either we do them all or nothing.