address review comments

index.bs

@@ -2978,7 +2978,7 @@ To <dfn>await a navigation</dfn> given |navigable|, |request|, |wait condition|,
 browsingContext.Locator = (
    browsingContext.AccessibilityLocator /
    browsingContext.CssLocator /
-   browsingContext.ContainerLocator /
+   browsingContext.ContextLocator /
    browsingContext.InnerTextLocator /
    browsingContext.XPathLocator
 )
@@ -2996,8 +2996,8 @@ browsingContext.CssLocator = {
    value: text
 }
 
-browsingContext.ContainerLocator = {
-  type: "container",
+browsingContext.ContextLocator = {
+  type: "context",
   value: {
     context: text,
   }
@@ -3803,7 +3803,7 @@ To <dfn>locate nodes using CSS</dfn> with given |navigable|, |context nodes|,
 </div>
 
 <div algorithm="locate the container element">
-To <dfn>locate the container element</dfn> with given |navigable|:
+To <dfn>locate the container element</dfn> given |navigable|:
 
 1. Let |returned nodes| be an empty [=/list=].
 
@@ -4081,18 +4081,25 @@ The [=remote end steps=] with |session| and |command parameters| are:
          1. Let |result nodes| be [=locate nodes using accessibility attributes=]
             given |context nodes|, |selector|, and |maximum returned node count|.
 
-      <dt>|type| is the string "<code>container</code>"
+      <dt>|type| is the string "<code>context</code>"
       <dd>
 
          1. If |start nodes parameter| is not null,
             return [=error=] with [=error code=] "<code>invalid argument</code>".
 
          1. Let |selector| be |locator|["<code>value</code>"].
 
-         1. Let |child navigable| be |selector|["<code>context</code>"].
+         1. Let |context id| be |selector|["<code>context</code>"].
+
+         1. Let |child navigable| be the result of [=trying=] to [=get a navigable=] with |context id|.
+
+         1. If |child navigable|'s [=navigable/parent=] is not |navigable|,
+            return [=error=] with [=error code=] "<code>invalid argument</code>".
 
          1. Let |result nodes| be [=locate the container element=] given |child navigable|.
 
+         1. Assert: For each |node| in |result nodes|, |node|'s [=/node navigable=] is |navigable|.
+
 1. Assert: |maximum returned node count| is null or [=list/size=] of |result nodes| is less
    than or equal to |maximum returned node count|.