emerge wants to reinstall chromium

About a fortnight ago I removed chromium in favour of midori.
I used # emerge unemerge chromium.
Then I instructed my computer to clean. Nothing was found to clean.
Tonight when I went to update my system I find emerge wants to reinstall chromium.
After finding the system wanted to reinstall chromium I used # emerge -C chomium and # emerge clean.
Nothing was found to remove, or clean.
And still it persists wanting to reinstall chromium.
This creates my three questions.
1/ How do I stop my computer installing chromium.
2/ What must I do to completely remove chromium, and
3/ How do I do select the files to be updated ?
Sorry to be a pain.

You can put this into <</etc/portage/profile/package.provided>>
But in this file you must put this by version. Like this:


But if will be new version, you must add this too.

I am absolutely delighted with your information
I assume if there is a new version I must add it too, and eventually it wll go through emerge clean