slow start up, NaCl errors

Since a long time, I noticed that Chrome took a long time to start up.
Today I launched it from the terminal to see what's happening and I see some NaCl errors:

```
$ flatpak run com.google.Chrome
[2 preload-host-spawn-strategy] Running: /app/bin/zypak-helper child - /app/extra/chrome --type=zygote --enable-crashpad --crashpad-handler-pid=19 --enable-crash-reporter=,unknown --change-stack-guard-on-fork=enable
Stub sandbox ignoring command: /app/extra/nacl_helper
[2:2:1118/101759.185058:ERROR:nacl_fork_delegate_linux.cc(329)] Bad NaCl helper startup ack (0 bytes)
Gtk-Message: 10:18:01.682: Failed to load module "canberra-gtk-module"
Gtk-Message: 10:18:01.682: Failed to load module "canberra-gtk-module"
[54:54:1118/101802.301761:ERROR:sandbox_linux.cc(374)] InitializeSandbox() called with multiple threads in process gpu-process.
[2:2:1118/101802.627453:ERROR:nacl_browser.cc(312)] Failed to open NaCl IRT file "/app/extra/nacl_irt_x86_64.nexe": -4
[2:81:1118/101825.769329:ERROR:chrome_browser_main_extra_parts_metrics.cc(230)] crbug.com/1216328: Checking Bluetooth availability started. Please report if there is no report that this ends.
[2:81:1118/101825.769405:ERROR:chrome_browser_main_extra_parts_metrics.cc(233)] crbug.com/1216328: Checking Bluetooth availability ended.
[2:81:1118/101825.769418:ERROR:chrome_browser_main_extra_parts_metrics.cc(236)] crbug.com/1216328: Checking default browser status started. Please report if there is no report that this ends.
[2:81:1118/101825.778612:ERROR:chrome_browser_main_extra_parts_metrics.cc(240)] crbug.com/1216328: Checking default browser status ended.
[1118/101832.302740:ERROR:scoped_ptrace_attach.cc(27)] ptrace: Operation not permitted (1)
[117:29:1118/101844.095711:ERROR:command_buffer_proxy_impl.cc(125)] ContextResult::kTransientFailure: Failed to send GpuControl.CreateCommandBuffer.
[117:12:1118/101844.095967:ERROR:command_buffer_proxy_impl.cc(125)] ContextResult::kTransientFailure: Failed to send GpuControl.CreateCommandBuffer.
[113:11:1118/101844.105093:ERROR:command_buffer_proxy_impl.cc(125)] ContextResult::kTransientFailure: Failed to send GpuControl.CreateCommandBuffer.
[2:2:1118/101844.105684:ERROR:gpu_process_host.cc(979)] GPU process exited unexpectedly: exit_code=512
[203:203:1118/101844.194736:ERROR:sandbox_linux.cc(374)] InitializeSandbox() called with multiple threads in process gpu-process.
```