LibWebView+WebContent: Notify UI process about WebContent PID explicitly

On Serenity, it's not trivial to extract the peer pid from a socket that
is created by SystemServer and then passed to a forked service process.
This patch adds an API to let the WebContent process notify the UI
directly, which makes the WebContent process show up in the Serenity
port's TaskManagerWidget. It seems that we will need to do something of
this sort in order to properly gather metrics on macOS as well, due to
the way that self mach ports work.

Ladybird/HelperProcess.cpp

@@ -96,8 +96,6 @@ ErrorOr<NonnullRefPtr<WebView::WebContentClient>> launch_web_content_process(
         dbgln();
     }
 
-    WebView::ProcessManager::the().add_process(WebView::ProcessType::WebContent, child_pid);
-
     return new_client;
 }
 

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

@@ -122,6 +122,7 @@ shared_library("LibWebView") {
     "Database.cpp",
     "History.cpp",
     "InspectorClient.cpp",
+    "ProcessHandle.cpp",
     "ProcessManager.cpp",
     "RequestServerAdapter.cpp",
     "SearchEngine.cpp",

Userland/Libraries/LibWebView/CMakeLists.txt

@@ -6,6 +6,7 @@ set(SOURCES
     Database.cpp
     History.cpp
     InspectorClient.cpp
+    ProcessHandle.cpp
     ProcessManager.cpp
     RequestServerAdapter.cpp
     SearchEngine.cpp

Userland/Libraries/LibWebView/Forward.h

@@ -21,6 +21,7 @@ class WebContentClient;
 
 struct Attribute;
 struct CookieStorageKey;
+struct ProcessHandle;
 struct SearchEngine;
 struct SocketPair;
 

Userland/Libraries/LibWebView/ProcessHandle.cpp

@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) 2024, Andrew Kaster <akaster@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibIPC/Decoder.h>
+#include <LibIPC/Encoder.h>
+#include <LibWebView/ProcessHandle.h>
+
+template<>
+ErrorOr<void> IPC::encode(IPC::Encoder& encoder, WebView::ProcessHandle const& handle)
+{
+    TRY(encoder.encode(handle.pid));
+    return {};
+}
+
+template<>
+ErrorOr<WebView::ProcessHandle> IPC::decode(IPC::Decoder& decoder)
+{
+    auto pid = TRY(decoder.decode<pid_t>());
+    return WebView::ProcessHandle { pid };
+}

Userland/Libraries/LibWebView/ProcessHandle.h

@@ -0,0 +1,25 @@
+/*
+ * Copyright (c) 2024, Andrew Kaster <akaster@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Types.h>
+#include <LibIPC/Forward.h>
+
+namespace WebView {
+
+struct ProcessHandle {
+    // FIXME: Use mach_port_t on macOS/Hurd and HANDLE on Windows.
+    pid_t pid;
+};
+
+}
+
+template<>
+ErrorOr<void> IPC::encode(IPC::Encoder&, WebView::ProcessHandle const&);
+
+template<>
+ErrorOr<WebView::ProcessHandle> IPC::decode(IPC::Decoder&);

Userland/Libraries/LibWebView/WebContentClient.cpp

@@ -5,6 +5,7 @@
  */
 
 #include "WebContentClient.h"
+#include "ProcessManager.h"
 #include "ViewImplementation.h"
 #include <LibWeb/Cookie/ParsedCookie.h>
 
@@ -33,6 +34,12 @@ void WebContentClient::unregister_view(u64 page_id)
     m_views.remove(page_id);
 }
 
+void WebContentClient::notify_process_information(WebView::ProcessHandle const& handle)
+{
+    dbgln_if(SPAM_DEBUG, "handle: WebContentClient::NotifyProcessInformation! pid={}", handle.pid);
+    ProcessManager::the().add_process(ProcessType::WebContent, handle.pid);
+}
+
 void WebContentClient::did_paint(u64 page_id, Gfx::IntRect const& rect, i32 bitmap_id)
 {
     if (auto view = view_for_page_id(page_id); view.has_value())

Userland/Libraries/LibWebView/WebContentClient.h

@@ -37,6 +37,7 @@ public:
 private:
     virtual void die() override;
 
+    virtual void notify_process_information(WebView::ProcessHandle const&) override;
     virtual void did_paint(u64 page_id, Gfx::IntRect const&, i32) override;
     virtual void did_finish_loading(u64 page_id, URL::URL const&) override;
     virtual void did_update_url(u64 page_id, URL::URL const& url, Web::HTML::HistoryHandlingBehavior history_behavior) override;

Userland/Services/WebContent/ConnectionFromClient.cpp

@@ -59,6 +59,7 @@ ConnectionFromClient::ConnectionFromClient(NonnullOwnPtr<Core::LocalSocket> sock
     , m_page_host(PageHost::create(*this))
 {
     m_input_event_queue_timer = Web::Platform::Timer::create_single_shot(0, [this] { process_next_input_event(); });
+    async_notify_process_information({ ::getpid() });
 }
 
 void ConnectionFromClient::die()

Userland/Services/WebContent/WebContentClient.ipc

@@ -15,9 +15,12 @@
 #include <LibWeb/Page/Page.h>
 #include <LibWebView/Attribute.h>
 #include <LibWebView/SocketPair.h>
+#include <LibWebView/ProcessHandle.h>
 
 endpoint WebContentClient
 {
+    notify_process_information(WebView::ProcessHandle handle) =|
+
     did_start_loading(u64 page_id, URL::URL url, bool is_redirect) =|
     did_finish_loading(u64 page_id, URL::URL url) =|
     did_update_url(u64 page_id, URL::URL url, Web::HTML::HistoryHandlingBehavior history_behavior) =|