LibIPC: Chunk sent file descriptors by MAX_TRANSFER_FDS

This limitation of the underlying Unix socket implementation can
cause IPC failures on pages with tons of images and network requests.

Modify the code called from TransportSocket's send thread to limit the
number of fds to MAX_TRANSFER_FDS, and ensure that we will keep sending
as long as we have either bytes or file descriptors to send.

Libraries/LibIPC/TransportSocket.cpp

@@ -46,7 +46,12 @@ SendQueue::BytesAndFds SendQueue::peek(size_t max_bytes)
     auto bytes_to_send = min(max_bytes, m_stream.used_buffer_size());
     result.bytes.resize(bytes_to_send);
     m_stream.peek_some(result.bytes);
-    result.fds = m_fds;
+
+    if (m_fds.size() > 0) {
+        auto fds_to_send = min(m_fds.size(), Core::LocalSocket::MAX_TRANSFER_FDS);
+        result.fds = Vector<int> { m_fds.span().slice(0, fds_to_send) };
+        // NOTE: This relies on a subsequent call to discard to actually remove the fds from m_fds
+    }
     return result;
 }
 
@@ -287,7 +292,7 @@ TransportSocket::ShouldShutdown TransportSocket::read_as_many_messages_as_possib
         }
 
         auto bytes_read = maybe_bytes_read.release_value();
-        if (bytes_read.is_empty()) {
+        if (bytes_read.is_empty() && received_fds.is_empty()) {
             should_shutdown = true;
             break;
         }