vulkan: Hook up image upload mechanism to env variables

Instead of having to decie at compile-time, check if
GSK_RENDERING=staging-image was given, and if so, select the staging
image upload mode.

gsk/gskvulkanimage.c

@@ -316,16 +316,10 @@ gsk_vulkan_image_new_from_data (GdkVulkanContext  *context,
                                 gsize              height,
                                 gsize              stride)
 {
-  switch (GSK_VULKAN_UPLOAD_IMAGE_DEFAULT)
+  if (GSK_RENDER_MODE_CHECK (STAGING_IMAGE))
-    {
-    default:
-      g_assert_not_reached ();
-      /* fall through */
-    case GSK_VULKAN_UPLOAD_DIRECTLY:
-      return gsk_vulkan_image_new_from_data_directly (context, command_buffer, data, width, height, stride);
-    case GSK_VULKAN_UPLOAD_VIA_STAGING_IMAGE:
     return gsk_vulkan_image_new_from_data_via_staging_image (context, command_buffer, data, width, height, stride);
-    }
+  else
+    return gsk_vulkan_image_new_from_data_directly (context, command_buffer, data, width, height, stride);
 }
 
 void

gsk/gskvulkanimageprivate.h

@@ -5,14 +5,6 @@
 
 G_BEGIN_DECLS
 
-/* Modify here for benchmarking */
-#define GSK_VULKAN_UPLOAD_IMAGE_DEFAULT GSK_VULKAN_UPLOAD_DIRECTLY
-
-typedef enum {
-  GSK_VULKAN_UPLOAD_DIRECTLY,
-  GSK_VULKAN_UPLOAD_VIA_STAGING_IMAGE
-} GstkVulkanImageUpload;
-
 typedef struct _GskVulkanImage GskVulkanImage;
 
 GskVulkanImage *        gsk_vulkan_image_new_from_data                  (GdkVulkanContext       *context,