Verify checksum on adblock list load from component

[ShivanKaul]

Related to brave/brave-core-crx-packager#806, to be maximally safe that an adblock list hasn't gotten corrupted somewhere in the process of reaching the user, we should verify the checksum before actually loading into brave-core. Note that we can only do this for certain adblock lists, the ones that have checksums in the first place.

[bbondy]

Could we up this priority for checksums @ShivanKaul ? I think a check could be added pretty painlessly somewhere around here: https://github.com/brave/adblock-resources/blob/master/index.js#L7

[bbondy]

Update: I see this is for the brave-core side, I think that's OK to be lower priority as is now so long as the checksums are being made in a place similar to the one I mentioned above when packaging them into crx files.

[ShivanKaul]

Yes, exactly.