Speed up expected_font_names

In expected_font_names we do a deep copy of the font because we're going to modify it
and we don't want to mess up further tests. But for big fonts this is very slow, and
we use expected_font_names a few times. We don't need glyf and gvar and GPOS and
everything else to work out what names the font should have. Instead, let's only copy
the tables that we need to run build_name_table.

(PR #4765)

Lib/fontbakery/checks/googlefonts/conditions.py

@@ -4,6 +4,8 @@
 import re
 import yaml
 
+from fontTools.ttLib.ttFont import TTFont
+
 from fontbakery.callable import condition
 from fontbakery.testable import Font, CheckRunContext
 from fontbakery.constants import (
@@ -285,7 +287,6 @@ def remote_styles(font):
     a given family as currently hosted at Google Fonts.
     """
     from fontbakery.utils import download_file
-    from fontTools.ttLib import TTFont
     import json
     import requests
 
@@ -487,7 +488,10 @@ def expected_font_names(ttFont, ttFonts):
     from copy import deepcopy
 
     siblings = [f for f in ttFonts if f != ttFont]
-    font_cp = deepcopy(ttFont)
+    font_cp = TTFont()
+    for table in ["fvar", "name", "STAT", "OS/2", "post", "head"]:
+        if table in ttFont:
+            font_cp[table] = deepcopy(ttFont[table])
     build_name_table(font_cp, siblings=siblings)
     if "fvar" in font_cp:
         build_fvar_instances(font_cp)