Deprecate the type field on Network.Initiator

This marks the field as optional and no longer sets it, so the CDDL continues to
match existing implementations, but it's no longer required to set it.

index.bs

@@ -5743,32 +5743,28 @@ To <dfn>deserialize header</dfn> given |protocol header|:
 
 <pre class="cddl local-cddl">
 network.Initiator = {
-    type: "parser" / "script" / "preflight" / "other",
     ? columnNumber: js-uint,
     ? lineNumber: js-uint,
     ? stackTrace: script.StackTrace,
-    ? request: network.Request
+    ? request: network.Request,
+    ? type: "parser" / "script" / "preflight" / "other"
 };
 </pre>
 
 The <code>network.Initiator</code> type represents the source of a network
 request.
 
+Note: The <code>type</code> field is included in the definition for backwards
+compatibility, but is no longer set by the [=get the initiator=] steps, and will
+be removed in a future revision of this specification. Its use is expected to be
+replaced by <code>initiatorType</code> and <code>destination</code> on
+<code>network.RequestData</code>.
+
 <div algorithm>
 To <dfn>get the initiator</dfn> given |request|:
 
 1. Let |request id| be |request|'s [=request id=].
 
-1. Let |type| be "<code>other</code>".
-
-1. If |request| is a [=CORS-Preflight Request=], set |type| to
-   "<code>preflight</code>".
-
-1. TODO: Get the |type|. It's not quite clear how this ought to work; the CDP
-   data depends on whether the navigation was kicked off by the parser or by
-   script (so e.g. inserting an image from script causes the initiator to be
-   "<code>script</code>"), but that doesn't correspond to anything in Fetch.
-
 1. If |request|'s [=request/initiator type=] is "<code>fetch</code>" or
    "<code>xmlhttprequest</code>":
 
@@ -5784,13 +5780,12 @@ To <dfn>get the initiator</dfn> given |request|:
   TODO: Chrome includes the current parser position as column number / line
   number for parser-inserted resources.
 
-1. Return a [=/map=] matching the <code>network.Initiator</code> production, with
-   the <code>type</code> field set to |type|, the <code>columnNumber</code>
-   field set to |column number| if it's not null, or omitted otherwise, the
-   <code>lineNumber</code> field set to |line number| if it's not null, or
-   omitted otherwise, the <code>stackTrace</code> field set to |stack trace| if
-   it's not null, or omitted otherwise, and the <code>request</code> field set
-   to |request id|.
+1. Return a [=/map=] matching the <code>network.Initiator</code> production, the
+   <code>columnNumber</code> field set to |column number| if it's not null, or
+   omitted otherwise, the <code>lineNumber</code> field set to |line number| if
+   it's not null, or omitted otherwise, the <code>stackTrace</code> field set to
+   |stack trace| if it's not null, or omitted otherwise, and the
+   <code>request</code> field set to |request id|.
 
 </div>