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".

Meta/gn/secondary/Userland/Libraries/LibWebView/BUILD.gn

@@ -123,6 +123,7 @@ shared_library("LibWebView") {
     "InspectorClient.cpp",
     "RequestServerAdapter.cpp",
     "SearchEngine.cpp",
+    "SocketPair.cpp",
     "SourceHighlighter.cpp",
     "URL.cpp",
     "UserAgent.cpp",