Update "emulation.setLocaleOverride" to also override "Accept-Language" header.

Author: lutien

index.bs

@@ -9635,18 +9635,23 @@ navigables|:
    navigables. In that case it's unclear in which order to override the headers.
 
 1. [=Update headers=] with |request| and |session|'s
-   [=session/extra headers=]' [=extra headers/default headers=]
+   [=session/extra headers=]' [=extra headers/default headers=].
 
 1. Let |user context headers| be |session|'s [=session/extra headers=]'
    [=extra headers/user context headers=].
 
+1. Let |accept language header override| be a null.
+
 1. For |navigable| in |related navigables|:
 
   1. Let |user context| be |navigable|'s [=associated user context=].
 
   1. If |user context headers| [=map/contains=] |user context|
      then [=update headers=] with |request| and
-     |user context headers|[|user context|]
+     |user context headers|[|user context|].
+
+   1. If [=locale overrides map=] [=map/contains=] |user context|,
+      set |accept language header override| to [=/header=] ("Accept-Language", [=locale overrides map=][|user context|]).
 
 1. Let |navigable headers| be |session|'s [=session/extra headers=]'
    [=extra headers/navigable headers=].
@@ -9659,6 +9664,17 @@ navigables|:
   1. If |navigable headers| contains |top-level traversable|
      [=update headers=] with |request| and |navigable headers|[|top-level traversable|].
 
+  1. If [=locale overrides map=] [=map/contains=] |top-level traversable|,
+     set |accept language header override| to [=/header=] ("Accept-Language", [=locale overrides map=][|top-level traversable|]).
+
+1. If |accept language header override| is not null:
+
+   1. Let |language override headers| be an empty [=/header list=].
+
+   1. Append |accept language header override| to |language override headers|.
+
+   1. [=Update headers=] with |request| and |language override headers|.
+
 </div>
 
 <div algorithm="remote end steps for network.setExtraHeaders">