[mutter] renderer-native: Actually use shadow fb when using software rendering

[Jonas Ådahl <jadahl src gnome org>]

commit 437f6b3d59f2102f5974bfc430176725f2ed67c2
Author: Jonas Ådahl <jadahl gmail com>
Date:   Wed Sep 25 16:34:43 2019 +0200

    renderer-native: Actually use shadow fb when using software rendering
    
    The commit 'renderer/native: Use shadow fb on software GL if preferred'
    attempted to force using a shadow fb when using llvmpipe in order to
    speed up blending, but instead only did so when llvmpipe AND the drm
    device explicityl asked for it.
    
    Now instead always force it for llvmpipe and other software rendering
    backends, and otherwise just query the drm device (i.e.
    DRM_CAP_DUMB_PREFER_SHADOW).
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/807

 src/backends/native/meta-renderer-native.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/src/backends/native/meta-renderer-native.c b/src/backends/native/meta-renderer-native.c
index 5c01375c8..21d00502c 100644
--- a/src/backends/native/meta-renderer-native.c
+++ b/src/backends/native/meta-renderer-native.c
@@ -3213,11 +3213,11 @@ should_force_shadow_fb (MetaRendererNative *renderer_native,
     case COGL_GPU_INFO_ARCHITECTURE_SANDYBRIDGE:
     case COGL_GPU_INFO_ARCHITECTURE_SGX:
     case COGL_GPU_INFO_ARCHITECTURE_MALI:
-      return FALSE;
+      break;
     case COGL_GPU_INFO_ARCHITECTURE_LLVMPIPE:
     case COGL_GPU_INFO_ARCHITECTURE_SOFTPIPE:
     case COGL_GPU_INFO_ARCHITECTURE_SWRAST:
-      break;
+      return TRUE;
     }
 
   kms_fd = meta_gpu_kms_get_fd (primary_gpu);