[paint] Don't use extents in hb-view

Let the clipbox do its magic. Currently works for ft backend only.

src/hb-ft-colr.hh

@@ -465,7 +465,6 @@ hb_ft_paint_glyph_colr (hb_font_t *font,
                                         clip_box.top_right.y);
     else
     {
-      /* XXX Untested. */
       auto *extents_funcs = hb_paint_extents_get_funcs ();
       hb_paint_extents_context_t extents_data;
       hb_ft_paint_context_t c (ft_font, font,

util/helper-cairo-user.hh

@@ -489,13 +489,6 @@ render_color_glyph (cairo_scaled_font_t  *scaled_font,
 
   hb_font_paint_glyph (font, glyph, get_cairo_paint_funcs (), cr, palette, color);
 
-  hb_glyph_extents_t hb_extents;
-  hb_font_get_glyph_extents (font, glyph, &hb_extents);
-  extents->x_bearing = (double) hb_extents.x_bearing / x_scale;
-  extents->y_bearing = (double)-hb_extents.y_bearing / y_scale;
-  extents->width     = (double) hb_extents.width     / x_scale;
-  extents->height    = (double)-hb_extents.height    / y_scale;
-
   return CAIRO_STATUS_SUCCESS;
 }