#3421 - Do root rewrite before rewriting to translated page

#3299 - Redirect for missing translations

There are parameters that influence rewrite behavior when requesting a web page:

1) accept-language header and availabity of translated pages
2) agent (may rewrite to browser specific page for downloads or documentation)

In case there exists a translation set,  for example Mexican (es-MX), with a
page is missing that has (2) agent specific rewrite, it will first be assumed
that the translation is availble (bcause the folder /es_MX/ exists). Then the
rewrite will be made to the agent specific page, for example /es_MX/firefox.

As a result of this, a user/browser configured with accept-languaget es-MX will
visit adblockplus.org - get rewritten to /es_MX/ - and subsequently get
rewritten to /es_MX/firefox which results in a 404.

This commit handles this by moving the (2) agent rewrite to occur before the
checking of available translations. The same user/browser will now visit
adblockplus.org - get rewritten to /firefox - and then fall back to seeing
the page in Spanish (language fallback), or in case the language is missing
completely, English (default locale).

[f.nicolaisen, 2017-09-08 13:57:38]

This was hotfixed to production yesterday. I'm not planning to make new patch
sets (unless you got any ideas).

[mathias, 2017-09-08 19:10:33]

I think there are two reasons nobody replied thus far:

1. You used the wrong e-mail addresses for every reviewer except myself (yeah I
know, having to remember that stuff is one of the reasons Rietveld and upload.py
suck donkey balls). I took the liberty and fix that for ya.

2. I don't understand what exactly this patch-set is supposed to solve (I guess
fixing Accept-Language handling, in which case that should be reflected in the
commit/patch message, instead of the currently rather pointless description) and
how it does that. I've read the ticket, but I wonder how something that is the
`last` rewrite can still work as expected when the language specific stuff is
handled later on?

[f.nicolaisen, 2017-09-11 07:13:35]

On 2017/09/08 19:10:33, mathias wrote:
> I think there are two reasons nobody replied thus far:
> 
> 1. You used the wrong e-mail addresses for every reviewer except myself (yeah
I
> know, having to remember that stuff is one of the reasons Rietveld and
upload.py
> suck donkey balls). I took the liberty and fix that for ya.

Thanks! I'm sure I added Fred by using the auto-complete feature in Rietveld..
next time I'll manually use the email addresses.

> 2. I don't understand what exactly this patch-set is supposed to solve (I
guess
> fixing Accept-Language handling, in which case that should be reflected in the
> commit/patch message, instead of the currently rather pointless description)
and
> how it does that. I've read the ticket, but I wonder how something that is the
> `last` rewrite can still work as expected when the language specific stuff is
> handled later on?

Gotcha. I'll work on improving the message.

[mathias, 2017-09-11 15:12:46]

LGTM.