headless: Add devtools discovery page

headless/BUILD.gn

Index: headless/BUILD.gn
diff --git a/headless/BUILD.gn b/headless/BUILD.gn
index f31584f924ae7c2d55af6062a9ce70eb5f1f2d49..a388908a17363256822740db962251d5fd30a021 100644
--- a/headless/BUILD.gn
+++ b/headless/BUILD.gn
@@ -3,6 +3,7 @@
 # found in the LICENSE file.
 
 import("//testing/test.gni")
+import("//tools/grit/grit_rule.gni")
 import("//tools/grit/repack.gni")
 
 group("headless") {
@@ -20,6 +21,7 @@ repack("pak") {
     "$root_gen_dir/content/app/strings/content_strings_en-US.pak",
     "$root_gen_dir/content/browser/tracing/tracing_resources.pak",
     "$root_gen_dir/content/content_resources.pak",
+    "$root_gen_dir/headless/headless_lib_resources.pak",
     "$root_gen_dir/net/net_resources.pak",
     "$root_gen_dir/ui/resources/ui_resources_100_percent.pak",
     "$root_gen_dir/ui/resources/webui_resources.pak",
@@ -28,6 +30,7 @@ repack("pak") {
   ]
 
   deps = [
+    ":headless_lib_resources_grit",
     "//content:resources",
     "//content/app/resources",
     "//content/app/strings",
@@ -43,6 +46,14 @@ repack("pak") {
   output = "$root_out_dir/headless_lib.pak"
 }
 
+grit("headless_lib_resources_grit") {
+  source = "lib/resources/headless_lib_resources.grd"
+  outputs = [
+    "grit/headless_lib_resources.h",
+    "$root_gen_dir/headless/headless_lib_resources.pak",
+  ]
+}
+
 static_library("headless_lib") {
   sources = [
     "lib/browser/headless_browser_context.cc",