Overloaded constructor of Date is slow

[zzemla]

With the overloaded Date constructor, creating new Date objects takes at least an order of magnitude longer on Firefox, blocking the main JS thread and causing performance issues on sites that process large number of dates.

This is largely due to the new URL(...) constructor being called multiple times to extract origin of each script on the stack during the new Date call, to check if Date hasTaintedMethod. The URL constructor is much slower than the Date constructor (about ~ 9x times slower).

I'm not sure why such check for tainted methods on Date object is important, but I would suggest to at least check if taintedOrigins is not-empty before doing

content-scope-scripts/src/utils.js

Line 392 in aff1438

const stackOrigins = getStackTraceOrigins(getStack())

to improve performance.

[jonathanKingston]

Thanks for the report, we've disabled this in Firefox for now before we look into the fix. Thanks for the detailed investigation here!