Fix macOS CI: use --single-process to bypass Mach port rendezvous failures

On macOS-14 CI runners, bootstrap_look_up for the MachPortRendezvousServer
fails for all child processes (renderer, network service) even with
--no-sandbox.  This is a bootstrap-namespace restriction in the CI
environment that --no-sandbox cannot override.

--single-process runs all Chromium subprocesses (renderer, network, GPU)
inside the browser process, eliminating subprocess spawning entirely and
removing any dependency on Mach port bootstrap IPC.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: linesight

unittests/main_test.py

@@ -159,8 +159,11 @@ def test_main(self):
             switches["in-process-gpu"] = ""
             switches["no-zygote"] = ""
         if MAC:
-            # Mach port rendezvous (IPC) fails for child processes on CI
-            # runners because the macOS sandbox blocks bootstrap_look_up.
+            # Mach port rendezvous (bootstrap_look_up) fails for child
+            # processes on macOS CI runners regardless of --no-sandbox.
+            # Single-process mode runs renderer/network/GPU in-process,
+            # eliminating all subprocess spawning and bootstrap IPC.
+            switches["single-process"] = ""
             switches["no-sandbox"] = ""
             switches["disable-gpu"] = ""
             switches["disable-gpu-compositing"] = ""

unittests/osr_test.py

@@ -127,8 +127,11 @@ def test_osr(self):
             switches["in-process-gpu"] = ""
             switches["no-zygote"] = ""
         if MAC:
-            # Mach port rendezvous (IPC) fails for child processes on CI
-            # runners because the macOS sandbox blocks bootstrap_look_up.
+            # Mach port rendezvous (bootstrap_look_up) fails for child
+            # processes on macOS CI runners regardless of --no-sandbox.
+            # Single-process mode runs renderer/network/GPU in-process,
+            # eliminating all subprocess spawning and bootstrap IPC.
+            switches["single-process"] = ""
             switches["no-sandbox"] = ""
             switches["in-process-gpu"] = ""
         browser_settings = {