[Ozone-Gbm] Explicitly crash if trying software rendering on GBM

ui/ozone/platform/dri/gbm_surface_factory.cc

Index: ui/ozone/platform/dri/gbm_surface_factory.cc
diff --git a/ui/ozone/platform/dri/gbm_surface_factory.cc b/ui/ozone/platform/dri/gbm_surface_factory.cc
index 9742541322c3c31aeaecade8db9277aef8d529f2..8109d0255c8bd6fc101c74d9e7aca416053695a5 100644
--- a/ui/ozone/platform/dri/gbm_surface_factory.cc
+++ b/ui/ozone/platform/dri/gbm_surface_factory.cc
@@ -21,6 +21,7 @@
 #include "ui/ozone/public/native_pixmap.h"
 #include "ui/ozone/public/overlay_candidates_ozone.h"
 #include "ui/ozone/public/ozone_switches.h"
+#include "ui/ozone/public/surface_ozone_canvas.h"
 #include "ui/ozone/public/surface_ozone_egl.h"
 
 namespace ui {
@@ -113,6 +114,12 @@ bool GbmSurfaceFactory::LoadEGLGLES2Bindings(
   return LoadDefaultEGLGLES2Bindings(add_gl_library, set_gl_get_proc_address);
 }
 
+scoped_ptr<SurfaceOzoneCanvas> GbmSurfaceFactory::CreateCanvasForWidget(
+    gfx::AcceleratedWidget widget) {
+  LOG(FATAL) << "Software rendering mode is not supported with GBM platform";
+  return nullptr;
+}
+
 scoped_ptr<SurfaceOzoneEGL> GbmSurfaceFactory::CreateEGLSurfaceForWidget(
     gfx::AcceleratedWidget widget) {
   scoped_refptr<GbmWrapper> gbm = GetGbmDevice(widget);