[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 8298ad60a9c73e03935fab1073633202c68b25a0..9cfa6d3e972db9ee4042081a25104b5030a6bdd5 100644
--- a/headless/BUILD.gn
+++ b/headless/BUILD.gn
@@ -197,6 +197,18 @@ action("gen_devtools_client_api") {
   ]
 }
 
+static_library("headless_fontconfig_utils") {
+  sources = [
+    "public/util/fontconfig.cc",
+    "public/util/fontconfig.h",
+  ]
+
+  deps = [
+    "//third_party/fontconfig",
+    "//third_party/freetype",
+  ]
+}
+
 static_library("headless_lib") {
   sources = [
     "app/headless_shell_switches.cc",
@@ -372,6 +384,10 @@ static_library("headless_lib") {
     deps += [ "//ui/ozone" ]
   }
 
+  if (headless_fontconfig_utils) {
+    deps += [ ":headless_fontconfig_utils" ]
+  }
+
   configs += [ ":headless_implementation" ]
 }