Allow for removing emulation (#1001)

### Step 1. 

Currently, passing emulation value of `null` behaves differently in different methods. This PR aligns the behavior to the following: passing `null` removes the emulation for the given scope. 

E.g. having pre-condition: NAVIGABLE locale emulation is set to NAVIGABLE_EMULATED_LOCALE and USER_CONTEXT locale emulation is set to USER_CONTEXT_EMULATED_LOCALE.
* The emulated locale of NAVIGABLE is NAVIGABLE_EMULATED_LOCALE.
* Call `emulation.setLocaleOverride(NAVIGABLE, null)`
* The emulated locale of NAVIGABLE is USER_CONTEXT_EMULATED_LOCALE.
* Call `emulation.setLocaleOverride(USER_CONTEXT, null)`.
* The emulated locale of NAVIGABLE is the default one.

Affected method:
* emulation.SetLocaleOverride
* emulation.SetScriptingEnabled
* emulation.SetTimezoneOverride

### Out of scope
The following methods require some extra effort, so it makes sense to get agreement on the approach and to land this PR first:
* emulation.SetForcedColorsModeThemeOverride
* emulation.SetGeolocationOverride
* emulation.SetScreenOrientationOverride


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<a href="https://pr-preview.s3.amazonaws.com/w3c/webdriver-bidi/pull/1001.html" title="Last updated on Sep 12, 2025, 11:34 AM UTC (e6ac810)">Preview</a> | <a href="https://pr-preview.s3.amazonaws.com/w3c/webdriver-bidi/1001/ef4a35d...e6ac810.html" title="Last updated on Sep 12, 2025, 11:34 AM UTC (e6ac810)">Diff</a>

Author: sadym-chromium

index.bs

@@ -3062,16 +3062,16 @@ An <dfn>unhandled prompt behavior struct</dfn> is a [=struct=] with:
 A [=remote end=] has a <dfn>viewport overrides map</dfn> which is a weak map between [=user contexts=] and [=viewport configuration=].
 
 A [=remote end=] has a <dfn>locale overrides map</dfn> which is a weak map between
-[=navigables=] or [=user contexts=] and string or null.
+[=navigables=] or [=user contexts=] and string.
 
 A [=remote end=] has a <dfn>timezone overrides map</dfn> which is a weak map between
-[=navigables=] or [=user contexts=] and string or null.
+[=navigables=] or [=user contexts=] and string.
 
 A [=remote end=] has an <dfn>unhandled prompt behavior overrides map</dfn> which is a
 weak map between [=user contexts=] and [=unhandled prompt behavior struct=].
 
 A [=remote end=] has a <dfn>scripting enabled overrides map</dfn> which is a weak
-map between [=navigables=] or [=user contexts=] and boolean or null.
+map between [=navigables=] or [=user contexts=] and boolean.
 
 ### Types ### {#module-browsingcontext-types}
 
@@ -5938,11 +5938,11 @@ The [=remote end steps=] with |command parameters| are:
    |command parameters|["<code>coordinates</code>"].
 
 1. If |command parameters| [=map/contains=] "<code>userContexts</code>"
-   and |command parameters| [=map/contains=] "<code>context</code>",
+   and |command parameters| [=map/contains=] "<code>contexts</code>",
    return [=error=] with [=error code=] [=invalid argument=].
 
 1. If |command parameters| doesn't [=map/contain=] "<code>userContexts</code>"
-   and |command parameters| doesn't [=map/contain=] "<code>context</code>",
+   and |command parameters| doesn't [=map/contain=] "<code>contexts</code>",
    return [=error=] with [=error code=] [=invalid argument=].
 
 1. Let |navigables| be a [=/set=].
@@ -6005,8 +6005,6 @@ locale on the given top-level traversables or user contexts.
 The [=DefaultLocale=] algorithm is implementation defined. A WebDriver-BiDi
 [=remote end=] must have an implementation that runs the following steps:
 
-1. Let |emulated locale| be null.
-
 1. Let |realm| be [=current Realm Record=].
 
 1. Let |environment settings| be the [=environment settings object=] whose
@@ -6022,15 +6020,12 @@ The [=DefaultLocale=] algorithm is implementation defined. A WebDriver-BiDi
 
     1. Let |user context| be |top-level traversable|'s [=associated user context=].
 
-    1. If [=locale overrides map=] [=map/contains=] |top-level traversable|, set
-       |emulated locale| to [=locale overrides map=][|top-level traversable|].
+    1. If [=locale overrides map=] [=map/contains=] |top-level traversable|, return
+       [=locale overrides map=][|top-level traversable|].
 
-    1. Otherwise, if [=locale overrides map=] [=map/contains=]
-       |user context|, set |emulated locale| to
+    1. If [=locale overrides map=] [=map/contains=] |user context|, return
        [=locale overrides map=][|user context|].
 
-1. If |emulated locale| is not null, return |emulated locale|.
-
 1. Return the result of implementation-defined steps in accordance with the
    requirements of the [=DefaultLocale=] specification.
 
@@ -6041,21 +6036,17 @@ The [=DefaultLocale=] algorithm is implementation defined. A WebDriver-BiDi
 The [=remote end steps=] with |command parameters| are:
 
 1. If |command parameters| [=map/contains=] "<code>userContexts</code>"
-   and |command parameters| [=map/contains=] "<code>context</code>",
+   and |command parameters| [=map/contains=] "<code>contexts</code>",
    return [=error=] with [=error code=] [=invalid argument=].
 
 1. If |command parameters| doesn't [=map/contain=] "<code>userContexts</code>"
-   and |command parameters| doesn't [=map/contain=] "<code>context</code>",
+   and |command parameters| doesn't [=map/contain=] "<code>contexts</code>",
    return [=error=] with [=error code=] [=invalid argument=].
 
-1. Let |emulated locale| be null.
+1. Let |emulated locale| be |command parameters|["<code>locale</code>"].
 
-1. If |command parameters| [=map/contains=] "<code>locale</code>":
-
-   1. Set |emulated locale| to |command parameters|["<code>locale</code>"].
-
-   1. If [=IsStructurallyValidLanguageTag=](|emulated locale|) returns false,
-      return [=error=] with [=error code=] [=invalid argument=].
+1. If |emulated locale| is not null and [=IsStructurallyValidLanguageTag=](|emulated locale|)
+   returns false, return [=error=] with [=error code=] [=invalid argument=].
 
 1. Let |navigables| be a [=/set=].
 
@@ -6074,7 +6065,9 @@ The [=remote end steps=] with |command parameters| are:
 
    1. For each |user context| of |user contexts|:
 
-      1. [=map/Set=] [=locale overrides map=][|user context|] to |emulated locale|.
+      1. If |emulated locale| is null, [=map/remove=] |user context| from [=locale overrides map=].
+
+      1. Otherwise, [=map/set=] [=locale overrides map=][|user context|] to |emulated locale|.
 
       1. [=list/For each=] |top-level traversable| of the list of all
          [=/top-level traversables=] whose [=associated user context=] is
@@ -6084,7 +6077,9 @@ The [=remote end steps=] with |command parameters| are:
 
 1. For each |navigable| of |navigables|:
 
-   1. [=map/Set=] [=locale overrides map=][|navigable|] to |emulated locale|.
+   1. If |emulated locale| is null, [=map/remove=] |navigable| from [=locale overrides map=].
+
+   1. Otherwise, [=map/set=] [=locale overrides map=][|navigable|] to |emulated locale|.
 
 1. Return [=success=] with data null.
 
@@ -6368,22 +6363,14 @@ The <dfn export>WebDriver BiDi scripting is enabled</dfn> steps given
 
 1. Let |top-level traversable| be |navigable|’s [=navigable/top-level traversable=].
 
-1. If [=scripting enabled overrides map=] contains |top-level traversable|:
-
-   1. If [=scripting enabled overrides map=][|top-level traversable|] is false,
-      return false.
-
-   1. Return true.
+1. If [=scripting enabled overrides map=] contains |top-level traversable|, return
+   [=scripting enabled overrides map=][|top-level traversable|]
 
 1. Let |user context| be  |top-level traversable|'s [=associated user context=].
 
 1. If [=scripting enabled overrides map=] contains |user context|, return
    [=scripting enabled overrides map=][|user context|].
 
-   1. If [=scripting enabled overrides map=][|user context|] is false, return false.
-
-   1. Return true.
-
 1. Return true.
 
 </div>
@@ -6393,19 +6380,14 @@ The <dfn export>WebDriver BiDi scripting is enabled</dfn> steps given
 The [=remote end steps=] with |command parameters| are:
 
 1. If |command parameters| [=map/contains=] "<code>userContexts</code>"
-   and |command parameters| [=map/contains=] "<code>context</code>",
+   and |command parameters| [=map/contains=] "<code>contexts</code>",
    return [=error=] with [=error code=] [=invalid argument=].
 
 1. If |command parameters| doesn't [=map/contain=] "<code>userContexts</code>"
-   and |command parameters| doesn't [=map/contain=] "<code>context</code>",
+   and |command parameters| doesn't [=map/contain=] "<code>contexts</code>",
    return [=error=] with [=error code=] [=invalid argument=].
 
-1. Let |emulated scripting enabled status| be null.
-
-1. If |command parameters| [=map/contains=] "<code>enabled</code>":
-
-   1. Set |emulated scripting enabled status| to
-      |command parameters|["<code>enabled</code>"].
+1. Let |emulated scripting enabled status| be |command parameters|["<code>enabled</code>"].
 
 1. If the <code>contexts</code> field of |command parameters| is present:
 
@@ -6415,7 +6397,10 @@ The [=remote end steps=] with |command parameters| are:
 
    1. For each |navigable| of |navigables|:
 
-      1. [=map/Set=] [=scripting enabled overrides map=][|navigable|] to
+      1. If |emulated scripting enabled status| is null, [=map/remove=] |navigable| from
+         [=scripting enabled overrides map=].
+
+      1. Otherwise, [=map/set=] [=scripting enabled overrides map=][|navigable|] to
          |emulated scripting enabled status|.
 
 1. If the <code>userContexts</code> field of |command parameters| is present:
@@ -6425,7 +6410,10 @@ The [=remote end steps=] with |command parameters| are:
 
    1. For each |user context| of |user contexts|:
 
-      1. [=map/Set=] [=scripting enabled overrides map=][|user context|] to
+      1. If |emulated scripting enabled status| is null, [=map/remove=] |user context| from
+         [=scripting enabled overrides map=].
+
+      1. Otherwise [=map/set=] [=scripting enabled overrides map=][|user context|] to
          |emulated scripting enabled status|.
 
 1. Return [=success=] with data null.
@@ -6502,22 +6490,19 @@ steps:
 The [=remote end steps=] with |command parameters| are:
 
 1. If |command parameters| [=map/contains=] "<code>userContexts</code>"
-   and |command parameters| [=map/contains=] "<code>context</code>",
+   and |command parameters| [=map/contains=] "<code>contexts</code>",
    return [=error=] with [=error code=] [=invalid argument=].
 
 1. If |command parameters| doesn't [=map/contain=] "<code>userContexts</code>"
-   and |command parameters| doesn't [=map/contain=] "<code>context</code>",
+   and |command parameters| doesn't [=map/contain=] "<code>contexts</code>",
    return [=error=] with [=error code=] [=invalid argument=].
 
-1. Let |emulated timezone| be null.
-
-1. If |command parameters| [=map/contains=] "<code>timezone</code>":
-
-   1. Set |emulated timezone| to |command parameters|["<code>timezone</code>"].
+1. Let |emulated timezone| be |command parameters|["<code>timezone</code>"].
 
-   1. If [=IsTimeZoneOffsetString=](|emulated timezone|) returns false and
-      [=AvailableNamedTimeZoneIdentifiers=] does not [=list/contain=]
-      |emulated timezone|, return [=error=] with [=error code=] [=invalid argument=].
+1. If |emulated timezone| is not null and
+   [=IsTimeZoneOffsetString=](|emulated timezone|) returns false and
+   [=AvailableNamedTimeZoneIdentifiers=] does not [=list/contain=]
+   |emulated timezone|, return [=error=] with [=error code=] [=invalid argument=].
 
 1. Let |navigables| be a [=/set=].
 
@@ -6536,8 +6521,10 @@ The [=remote end steps=] with |command parameters| are:
 
    1. For each |user context| of |user contexts|:
 
-      1. [=map/Set=] [=timezone overrides map=][|user context|] to
-         |emulated timezone|.
+      1. If |emulated timezone| is null, [=map/remove=] |user context| from
+         [=timezone overrides map=].
+
+      1. Otherwise, [=map/set=] [=timezone overrides map=][|user context|] to |emulated timezone|.
 
       1. [=list/For each=] |top-level traversable| of the list of all
          [=/top-level traversables=] whose [=associated user context=] is
@@ -6547,7 +6534,9 @@ The [=remote end steps=] with |command parameters| are:
 
 1. For each |navigable| of |navigables|:
 
-   1. [=map/Set=] [=timezone overrides map=][|navigable|] to |emulated timezone|.
+   1. If |emulated timezone| is null, [=map/remove=] |navigable| from [=timezone overrides map=].
+
+   1. Otherwise, [=map/set=] [=timezone overrides map=][|navigable|] to |emulated timezone|.
 
 1. Return [=success=] with data null.