[headless] Enable headless embedders to specify fonts.

headless/BUILD.gn

Index: headless/BUILD.gn
diff --git a/headless/BUILD.gn b/headless/BUILD.gn
index 719ee27900f1b89619513e535d12b2ca94dfdc20..49124bcf949f0fa88b03f30d4cda8d045a56b4eb 100644
--- a/headless/BUILD.gn
+++ b/headless/BUILD.gn
@@ -200,6 +200,20 @@ action("gen_devtools_client_api") {
   ]
 }
 
+if (headless_fontconfig_utils) {
+  static_library("headless_fontconfig_utils") {
+    sources = [
+      "public/util/fontconfig.cc",
+      "public/util/fontconfig.h",
+    ]
+
+    deps = [
+      "//third_party/fontconfig",
+      "//third_party/freetype",
+    ]
+  }
+}
+
 component("headless") {
   sources = [
     "app/headless_shell_switches.cc",
@@ -380,6 +394,10 @@ component("headless") {
     deps += [ "//ui/ozone" ]
   }
 
+  if (headless_fontconfig_utils) {
+    deps += [ ":headless_fontconfig_utils" ]
+  }
+
   configs += [ ":headless_implementation" ]
 }