Add missing header files to GN files

third_party/harfbuzz-ng/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/chrome_build.gni")
 import("//build/config/features.gni")
 import("//build/config/linux/pkg_config.gni")
 import("//build/config/ui.gni")
 import("//testing/libfuzzer/fuzzer_test.gni")
 
@@ skipping 85 matching lines @@
       "src/hb-ot-layout-gpos-table.hh",
       "src/hb-ot-layout-gsub-table.hh",
       "src/hb-ot-layout-gsubgpos-private.hh",
       "src/hb-ot-layout-private.hh",
       "src/hb-ot-layout.cc",
       "src/hb-ot-layout.h",
       "src/hb-ot-map-private.hh",
       "src/hb-ot-map.cc",
       "src/hb-ot-math-table.hh",
       "src/hb-ot-math.cc",
+      "src/hb-ot-math.h",
       "src/hb-ot-maxp-table.hh",
       "src/hb-ot-name-table.hh",
       "src/hb-ot-shape-complex-arabic-fallback.hh",
       "src/hb-ot-shape-complex-arabic-private.hh",
       "src/hb-ot-shape-complex-arabic-table.hh",
       "src/hb-ot-shape-complex-arabic.cc",
       "src/hb-ot-shape-complex-default.cc",
       "src/hb-ot-shape-complex-hangul.cc",
       "src/hb-ot-shape-complex-hebrew.cc",
       "src/hb-ot-shape-complex-indic-machine.hh",
@@ skipping 107 matching lines @@
 fuzzer_test("harfbuzz_fuzzer") {
   sources = [
     "fuzz/harfbuzz_fuzzer.cc",
   ]
   deps = [
     ":harfbuzz-ng",
   ]
   libfuzzer_options = [ "max_len=16800" ]
   seed_corpus = "fuzz/seed_corpus"
 }