[mutter] cogl/gl: Fix switch passthrough warnings

[Marge Bot <marge-bot src gnome org>]

commit c9125aba73ac3b500535af4fa43f35267477acb6
Author: Jonas Ådahl <jadahl gmail com>
Date:   Fri Mar 4 20:46:21 2022 +0100

    cogl/gl: Fix switch passthrough warnings
    
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2319>

 cogl/cogl/driver/gl/cogl-pipeline-fragend-glsl.c | 2 +-
 cogl/cogl/driver/gl/gles/cogl-driver-gles.c      | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)
---
diff --git a/cogl/cogl/driver/gl/cogl-pipeline-fragend-glsl.c 
b/cogl/cogl/driver/gl/cogl-pipeline-fragend-glsl.c
index d932a5cf56..d25419b9b5 100644
--- a/cogl/cogl/driver/gl/cogl-pipeline-fragend-glsl.c
+++ b/cogl/cogl/driver/gl/cogl-pipeline-fragend-glsl.c
@@ -534,7 +534,7 @@ add_arg (CoglPipelineShaderState *shader_state,
                                   swizzle);
           break;
         }
-      /* flow through */
+      G_GNUC_FALLTHROUGH;
     case COGL_PIPELINE_COMBINE_SOURCE_PRIMARY_COLOR:
       g_string_append_printf (shader_source, "cogl_color_in.%s", swizzle);
       break;
diff --git a/cogl/cogl/driver/gl/gles/cogl-driver-gles.c b/cogl/cogl/driver/gl/gles/cogl-driver-gles.c
index 1780c3fbeb..00f72fbab9 100644
--- a/cogl/cogl/driver/gl/gles/cogl-driver-gles.c
+++ b/cogl/cogl/driver/gl/gles/cogl-driver-gles.c
@@ -133,8 +133,7 @@ _cogl_driver_pixel_format_to_gl (CoglContext     *context,
           required_format = format;
           break;
         }
-      /* flow through */
-
+      G_GNUC_FALLTHROUGH;
       /* Just one 24-bit ordering supported */
     case COGL_PIXEL_FORMAT_RGB_888:
     case COGL_PIXEL_FORMAT_BGR_888:
@@ -155,6 +154,7 @@ _cogl_driver_pixel_format_to_gl (CoglContext     *context,
           gltype = GL_UNSIGNED_INT_2_10_10_10_REV_EXT;
           break;
         }
+      G_GNUC_FALLTHROUGH;
 #endif
     case COGL_PIXEL_FORMAT_BGRA_1010102:
     case COGL_PIXEL_FORMAT_BGRA_1010102_PRE: