Decouple use_system_harfbuzz=1 from is_chromeos=1 & is_linux build flags

third_party/harfbuzz-ng/BUILD.gn

Index: third_party/harfbuzz-ng/BUILD.gn
diff --git a/third_party/harfbuzz-ng/BUILD.gn b/third_party/harfbuzz-ng/BUILD.gn
index 4824a4f864bfcb16e24cc7571d7bbef7be739726..fcb3f0abebef0ce162eabf5084d946a28d5b22f6 100644
--- a/third_party/harfbuzz-ng/BUILD.gn
+++ b/third_party/harfbuzz-ng/BUILD.gn
@@ -6,26 +6,17 @@ import("//build/config/chrome_build.gni")
 import("//build/config/linux/pkg_config.gni")
 import("//build/config/ui.gni")
 
-# The GYP build supports system harfbuzz for non-official builds when using
-# pangoft2 1.31.0 or greater (which pulls it in).
-# TODO(brettw) we can consider doing this as well, although the benefit is
-# unclear and requires shelling out to a script to check the version.
-#
-# ChromeOS uses an up-to-date system one that we have control over, so we
-# don't want to bloat the binary more by including another copy.
-
 declare_args() {
-  # Since version 1.31.0, pangoft2 which we depend on pulls in harfbuzz
-  # anyways. However, we want to have control of the version of harfbuzz
-  # we use, so don't use system harfbuzz unless we are building for
-  # chrome os, where we have the system harfbuzz under control.
-  use_system_harfbuzz =
-      is_linux && is_chromeos && exec_script(pkg_config_script,
-                                             pkg_config_args + [
-                                                   "--atleast-version=1.31.0",
-                                                   "pangoft2",
-                                                 ],
-                                             "value")
+  # Only overriden by the official Chromium OS builds which are done
+  # against the Chromium OS SDK in a chroot. Should not be needed in any
+  # other configuration.
+  # We need to be controlling the version of HarfBuzz used by Blink, as
+  # the correctness and good performance of text processing is only
+  # guaranteed and supported against the version of HarfBuzz that is in
+  # third_party/harfbuzz-ng.  So, on all other platforms HarfBuzz is
+  # statically linked, on Chrome OS it is controlled as well, but part
+  # of the system.
+  use_system_harfbuzz = false
 }
 
 if (use_system_harfbuzz) {