LibWeb+WebContent: Spawn Worker processes from the chrome

Instead of spawning these processes from the WebContent process, we now
create them in the Browser chrome.

Part 1/N of "all processes are owned by the chrome".

Userland/Services/WebContent/WebContentClient.ipc

@@ -9,6 +9,7 @@
 #include <LibWeb/HTML/SelectItem.h>
 #include <LibWeb/Page/Page.h>
 #include <LibWebView/Attribute.h>
+#include <LibWebView/SocketPair.h>
 
 endpoint WebContentClient
 {
@@ -78,6 +79,8 @@ endpoint WebContentClient
 
     did_finish_text_test() =|
 
+    request_worker_agent() => (WebView::SocketPair sockets) // FIXME: Add required attributes to select a SharedWorker Agent
+
     inspector_did_load() =|
     inspector_did_select_dom_node(i32 node_id, Optional<Web::CSS::Selector::PseudoElement::Type> pseudo_element) =|
     inspector_did_set_dom_node_text(i32 node_id, String text) =|