headless: Add a small C++ example application

headless/BUILD.gn

Index: headless/BUILD.gn
diff --git a/headless/BUILD.gn b/headless/BUILD.gn
index 7f155ee2e080e1c520781bb5822be8ac047a6ac9..a5d6d8519feb92b6f133c4a626078377171a7595 100644
--- a/headless/BUILD.gn
+++ b/headless/BUILD.gn
@@ -259,6 +259,7 @@ group("headless_tests") {
 
   deps = [
     ":headless_browsertests",
+    ":headless_example",
     ":headless_unittests",
   ]
 }
@@ -379,3 +380,13 @@ executable("headless_shell") {
     "//headless:headless_shell_lib",
   ]
 }
+
+executable("headless_example") {
+  sources = [
+    "app/headless_example.cc",
+  ]
+
+  deps = [
+    "//headless:headless_shell_lib",
+  ]
+}