Provide the right size to GL when downloading. This fixes downloading
from GLMemory that where created for libav.
https://bugzilla.gnome.org/show_bug.cgi?id=744246
GST_DEBUG ("downloading texture %u using pbo %u",
gl_mem->tex_id, gl_mem->transfer_pbo);
- size = ((GstMemory *) gl_mem)->maxsize;
+ size = gst_gl_get_plane_data_size (&gl_mem->info, &gl_mem->valign,
+ gl_mem->plane);
plane_start = _find_plane_frame_start (gl_mem);
format = _gst_gl_format_from_gl_texture_type (gl_mem->tex_type);
type = GL_UNSIGNED_BYTE;