chrome_http_user_agent_settings.cc includes provisions to update Accept-Languages value when user preferences change, but I don't know whether it is used on Android: https://cs.chromium.org/chromium/src/chrome/browser/net/chrome_http_user_agent_settings.cc

We are not able to repro this issue on Chrome Stable:56.0.2924.87,55.0.2883.91 Chrome Beta:57.0.2987.88 Device:Nexus 5X/N2G47H

This issue looks similar to 
https://bugs.chromium.org/p/chromium/issues/detail?id=593515
https://bugs.chromium.org/p/chromium/issues/detail?id=369897

CC'ing devs from  issue 593515 

Chrome is expected to restart when the system locales change, which will cause it to read the configuration afresh. See  issue 35049  for the background there. If that's not happening, that's a regression. If it doesn't pick up the right config after the restart, that's also a regression.

+groby - Do you know how accept-language is generated?

I did a quick glance through the code and the only place I see it updated is in translate code:
https://cs.chromium.org/chromium/src/components/translate/core/browser/translate_prefs.cc?q=translate_prefs+package:%5Echromium$&l=409

Weird, yeah I confirmed that this issue available on M56, ja-JP is listed to the first place even if the Japanese is listed in the 2nd place in system language.

> #6

First, there are two source of accept-languages, the default accept-languages coming from resources, and the system language preference.

They are merged in pref_service_bridge.cc.

https://cs.chromium.org/chromium/src/chrome/browser/android/preferences/pref_service_bridge.cc?rcl=163d7ed981d080347b05a6ad4d47d0e2418f04e9&l=1088

then finally, fallback language is appended in a platform neutral way in net/http_util.cc

https://cs.chromium.org/chromium/src/net/http/http_util.cc?rcl=163d7ed981d080347b05a6ad4d47d0e2418f04e9&l=737

Looks like this is no longer available on ToT.

I just checked out and tested on the ToT Chrome with Android N and the accept-langauge is
en-US,ja-JP;q=0.8,ja;q=0.6,en;q=0.4

The fallback order may be still weird but server should use en-US as the first priority.

I wonder if the reason is https://chromiumcodereview.appspot.com/23923007

If I read this right, it adds a language to the language list when it's been marked for "never translate". 

That's... an interesting but understandable choice. That said, this should only happen when you click "never translate". And it certainly doesn't persist if you wipe out your settings. (I don't know what OP meant by 'wiping Chrome data' - if it includes wiping preferences, this shouldn't be the cause)

Oh translate may change the accept-language, I didn't know that.

Yeah, so there are three sources, default accept-languages, system languages and languages not to be translated.

My feeling is something like that translate should aware of system languages and don't offer translate to the language listed in system languages.

All,

Thanks for investigating this so quickly.

> #10

I don't recall clicking "never translate" but I might have and just not noticed. However, performing "reset translate settings" does not solve the issue.

By wiping Chrome data, I meant I tried "clear data" from "Clear browsing data" inside Chrome as well as Settings > Apps > Chrome > Storage > Manage Space > Clear All Data from the Android settings.

This is interesting. Can you check on desktop what your language preferences are in chrome://settings/languages? I tried a variation of this on my device (using Russian and English instead of Japanese and English) and noticed that my accept_language prefs from desktop seemed to be overriding my locale (e.g. when I'd change my Android locale to Russian I'd still get the English reddit.com site).

Something is definitely weird with the settings.

When I reproduced this on the second device, that account did have Japanese listed under settings/languages on desktop. I don't believe removing it from the language settings solved the issue as it persisted for multiple days on my Android device after I did so. Updating my system languages in Android after removing from settings/languages on desktop finally resolved the issue on this device.

Back to the first account & device this occurred with: Japanese was not listed under settings/languages on desktop last time I checked. I'll double check later today when I can get access to that desktop that has this account signed in. However, I've found a workaround the bug on Android. From a fresh Chrome install, I unchecked sync settings. Everything behaves as normal, only getting English. Re-enabling the syncing of settings causes pages to return back to Japanese. This account must have Japanese in it's settings. If it's not showing up in settings/languages on desktop that's a separate issue since it did show up for the second account.

To go back to English I unchecked sync settings again. This must be stored on disk somewhere? since a reboot was not sufficient. I needed to change my Android system languages for Chrome to refresh it's languages, mimicking the behavior above with the second account.

Assigning this to Leo who is experienced in Android.

I am composing a setting page for Clank users to update their accepted languages, and this bug should be fixed after that.

Fixed with the addition of language settings controls to Chrome on Android in M65.