[headless] Use version for product name and user agent.

headless/lib/browser/headless_browser_context_options.cc

Index: headless/lib/browser/headless_browser_context_options.cc
diff --git a/headless/lib/browser/headless_browser_context_options.cc b/headless/lib/browser/headless_browser_context_options.cc
index 2dd7939e26af2e08ecdd0f97753bfb2d8ea42744..f9fa8248e5b57f9fc7f05ccd470f3b29f6409fe9 100644
--- a/headless/lib/browser/headless_browser_context_options.cc
+++ b/headless/lib/browser/headless_browser_context_options.cc
@@ -35,6 +35,12 @@ HeadlessBrowserContextOptions::HeadlessBrowserContextOptions(
     HeadlessBrowser::Options* options)
     : browser_options_(options) {}
 
+const std::string& HeadlessBrowserContextOptions::product_name_and_version()
+    const {
+  return ReturnOverriddenValue(product_name_and_version_,
+                               browser_options_->product_name_and_version);
+}
+
 const std::string& HeadlessBrowserContextOptions::user_agent() const {
   return ReturnOverriddenValue(user_agent_, browser_options_->user_agent);
 }