emulation.setNetworkConditions:offline (#948)

First step addressing #776.
* Fail all the intercepted requests, WebSocket and WebTransport.
* Html spec: whatwg/html#11575
* Fetch spec: whatwg/fetch#1852

Author: sadym-chromium

index.bs

@@ -328,6 +328,12 @@ spec: RFC9110; urlPrefix: https://httpwg.org/specs/rfc9110.html
 spec: STREAMS; urlPrefix: https://streams.spec.whatwg.org/
   type: dfn
     text: ReadableStream; url: #readablestream
+spec: WebSockets; urlPrefix: https://websockets.spec.whatwg.org/
+  type: dfn
+    text: WebSocket; url: #websocket
+spec: WebTransport; urlPrefix: https://w3c.github.io/webtransport/
+  type: dfn
+    text: Cleanup WebTransport; url: #webtransport-cleanup
 </pre>
 
 <style>
@@ -766,7 +772,7 @@ The <dfn export>set of sessions for which an event is enabled</dfn> given |event
 
 1. Let |sessions| be a new [=/set=].
 
-1. For each |session| in [=active BiDI sessions=]:
+1. For each |session| in [=active BiDi sessions=]:
 
   1. If [=event is enabled=] with |session|, |event name| and |navigables|,
     append |session| to |sessions|.
@@ -1543,6 +1549,20 @@ A [=BiDi session=] has a
 A [=BiDi session=] has a <dfn>user context to proxy configuration map</dfn>, which is
 a [=/map=] between [=user contexts=] and [=proxy configuration=].
 
+An <dfn>emulated network conditions struct</dfn> is a [=struct=] with:
+* [=struct/item=] named <dfn id="emulated-network-conditions-struct-offline"
+  for="emulated-network-conditions-struct">offline</dfn> which is a boolean or null.
+
+A [=BiDi session=] has a <dfn for=session>emulated network conditions</dfn> which is
+a [=struct=] with an [=struct/item=] named <dfn
+for="emulated network conditions">default network conditions</dfn>, which is an
+[=emulated network conditions struct=] or null, an [=struct/item=] named
+<dfn for="emulated network conditions">user context network conditions</dfn>, which
+is a weak map between [=user contexts=] and [=emulated network conditions struct=],
+and a [=struct/item=] named
+<dfn for="emulated network conditions">navigable network conditions</dfn>, which is a
+weak map between [=navigables=] and [=emulated network conditions struct=].
+
 When a [=user context=] is [=set/remove|removed=] from the
 [=set of user contexts=], [=remove user context subscriptions=].
 
@@ -5930,6 +5950,7 @@ EmulationCommand = (
   emulation.SetForcedColorsModeThemeOverride //
   emulation.SetGeolocationOverride //
   emulation.SetLocaleOverride //
+  emulation.SetNetworkConditions //
   emulation.SetScreenOrientationOverride //
   emulation.SetScriptingEnabled //
   emulation.SetTimezoneOverride //
@@ -6276,6 +6297,128 @@ The [=remote end steps=] with |command parameters| are:
 
 </div>
 
+#### The emulation.setNetworkConditions Command ####  {#command-emulation-setNetworkConditions}
+
+The <dfn export for=commands>emulation.setNetworkConditions</dfn> command
+emulates specific network conditions for the given browsing context or for a user
+context.
+
+<dl>
+   <dt>Command Type</dt>
+   <dd>
+    <pre class="cddl" data-cddl-module="remote-cddl">
+      emulation.SetNetworkConditions = (
+        method: "emulation.setNetworkConditions",
+        params: emulation.setNetworkConditionsParameters
+      )
+
+      emulation.setNetworkConditionsParameters = {
+        networkConditions: emulation.NetworkConditions / null,
+        ? contexts: [+browsingContext.BrowsingContext],
+        ? userContexts: [+browser.UserContext],
+      }
+
+      emulation.NetworkConditions = emulation.NetworkConditionsOffline
+
+      emulation.NetworkConditionsOffline = {
+        type: "offline"
+      }
+    </pre>
+   </dd>
+   <dt>Result Type</dt>
+   <dd>
+    <code>
+     EmptyResult
+    </code>
+   </dd>
+</dl>
+
+<div algorithm>
+
+To <dfn>apply network conditions</dfn>:
+
+1. For each [=WebSocket=] object |webSocket|:
+
+  1. Let |realm| be |webSocket|'s [=relevant Realm=].
+
+  1. Let |environment settings| be the [=environment settings object=] whose
+     [=realm execution context=]'s Realm component is |realm|.
+
+  1. If the result of [=WebDriver BiDi network is offline=] with |environment settings| is true:
+
+     1. [=Fail the WebSocket connection=] |webSocket|.
+
+1. For each [=WebTransport=] object |webTransport|:
+
+  1. Let |realm| be |webSocket|'s [=relevant Realm=].
+
+  1. Let |environment settings| be the [=environment settings object=] whose
+     [=realm execution context=]'s Realm component is |realm|.
+
+  1. If the result of [=WebDriver BiDi network is offline=] with |environment settings| is true:
+
+     1. [=Cleanup WebTransport=] |webTransport|.
+
+</div>
+
+<div algorithm="remote end steps for emulation.setNetworkConditions">
+
+The [=remote end steps=] with |command parameters| and |session| are:
+
+1. If |command parameters| [=map/contains=] "<code>userContexts</code>"
+   and |command parameters| [=map/contains=] "<code>context</code>",
+   return [=error=] with [=error code=] [=invalid argument=].
+
+1. Let |emulated network conditions| be null.
+
+1. If |command parameters|["<code>networkConditions</code>"] is not null and
+      |command parameters|["<code>networkConditions</code>"]["<code>type</code>"]
+      equals "<code>offline</code>", set |emulated network conditions| to a new
+      [=emulated network conditions struct=] with
+      [=emulated-network-conditions-struct/offline=] set to true.
+
+1. If the <code>contexts</code> field of |command parameters| is present:
+
+   1. Let |navigables| be the result of [=trying=] to
+      [=get valid top-level traversables by ids=] with
+      |command parameters|["<code>contexts</code>"].
+
+   1. For each |navigable| of |navigables|:
+
+      1. If |emulated network conditions| is null, [=map/remove=] |navigable| from
+         |session|'s [=emulated network conditions=]'s
+         [=emulated network conditions/navigable network conditions=]
+
+      1. Otherwise, [=map/set=] |session|'s [=emulated network conditions=]'s
+         [=emulated network conditions/navigable network conditions=][|navigable|] to
+         |emulated network conditions|.
+
+1. If the <code>userContexts</code> field of |command parameters| is present:
+
+   1. Let |user contexts| be the result of [=trying=] to [=get valid user contexts=]
+      with |command parameters|["<code>userContexts</code>"].
+
+   1. For each |user context| of |user contexts|:
+
+      1. If |emulated network conditions| is null, [=map/remove=] |user context| from
+         |session|'s [=emulated network conditions=]'s
+         [=emulated network conditions/user context network conditions=].
+
+      1. Otherwise, [=map/set=] |session|'s [=emulated network conditions=]'s
+         [=emulated network conditions/user context network conditions=][|user context|]
+         to |emulated network conditions|.
+
+1. If |command parameters| doesn't [=map/contain=] "<code>userContexts</code>"
+   and |command parameters| doesn't [=map/contain=] "<code>context</code>",
+   [=map/set=] |session|'s [=emulated network conditions=]'s
+   [=emulated network conditions/default network conditions=] to |emulated network conditions|.
+
+1. [=Apply network conditions=].
+
+1. Return [=success=] with data null.
+
+</div>
+
 #### The emulation.setScreenOrientationOverride Command ####  {#command-emulation-setScreenOrientationOverride}
 
 The <dfn export for=commands>emulation.setScreenOrientationOverride</dfn> command
@@ -9684,6 +9827,60 @@ and |user context| are:
 
 </div>
 
+<div algorithm>
+The steps to <dfn>get emulated network conditions</dfn> given |related navigables|
+are:
+
+1. For each |navigable| of |related navigables|:
+
+   1. Let |top-level traversable| be |navigable|’s [=navigable/top-level traversable=].
+
+   1. Let |user context| be |top-level traversable|'s [=associated user context=].
+
+   1. For each |session| in [=active BiDi sessions=]:
+
+      1. If |session|'s [=emulated network conditions=]'s
+         [=emulated network conditions/navigable network conditions=]
+         [=map/contains=] |top-level traversable|, return |session|'s
+         [=emulated network conditions=]'s
+         [=emulated network conditions/navigable network conditions=][|top-level traversable|].
+
+   1. For each |session| in [=active BiDi sessions=]:
+
+      1. If |session|'s [=emulated network conditions=]'s
+         [=emulated network conditions/user context network conditions=]
+         [=map/contains=] |user context|, return |session|'s
+         [=emulated network conditions=]'s
+         [=emulated network conditions/user context network conditions=][|user context|].
+
+   1. For each |session| in [=active BiDi sessions=]:
+
+      1. If |session|'s [=emulated network conditions=]'s
+         [=emulated network conditions/default network conditions=] is not null,
+         return |session|'s [=emulated network conditions=]'s
+         [=emulated network conditions/default network conditions=].
+
+1. Return null.
+
+</div>
+
+<div algorithm>
+The <dfn export>WebDriver BiDi network is offline</dfn> steps given
+[=environment settings object=] |settings| are:
+
+1. Let |navigable| be |settings|'s [=relevant global object=]'s
+   <a>associated <code>Document</code></a>'s [=/node navigable=].
+
+1. Let |emulated network conditions| be the result of
+   [=get emulated network conditions=] with [|navigable|].
+
+1. If |emulated network conditions| is not null and |emulated network conditions|'s
+   [=emulated-network-conditions-struct/offline=] is true, return true.
+
+1. Return false.
+
+</div>
+
 <div algorithm>
 The [=remote end event trigger=] is the <dfn export>WebDriver BiDi before request sent</dfn> steps
 given [=/request=] |request|:
@@ -9793,8 +9990,17 @@ given [=/request=] |request|:
 
     Note: While waiting, no further processing of the request occurs.
 
+1. Let |emulated network conditions| be the result of
+   [=get emulated network conditions=] with |related navigables|.
+
+1. If |emulated network conditions| is not null and
+   |emulated network conditions|'s [=emulated-network-conditions-struct/offline=] is
+   true, return ([=network error=], "<code>complete</code>").
+
 1. Return (|response|, |response status|).
 
+Issue: Respect return value in Fetch's "HTTP-network-or-cache fetch" algorithm.
+
 </div>
 
 #### The network.fetchError Event #### {#event-network-fetchError}
@@ -13378,7 +13584,7 @@ The [=remote end event trigger=] is:
 Define the following [=console steps=] with |method|, |args|, and
 <var ignore>options</var>:
 
-1. For each |session| in [=active BiDI sessions=]:
+1. For each |session| in [=active BiDi sessions=]:
 
   1. If |method| is "<code>error</code>" or "<code>assert</code>", let |level| be
      "<code>error</code>". If |method| is "<code>debug</code>" or "<code>trace</code>"