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

headless/public/headless_browser_context.h

Index: headless/public/headless_browser_context.h
diff --git a/headless/public/headless_browser_context.h b/headless/public/headless_browser_context.h
index c913305bdbdb16055e460a564efc81f43ac85fad..4bdd7a51d7ea8d5b7dc6aced8350c3e237fbf1d4 100644
--- a/headless/public/headless_browser_context.h
+++ b/headless/public/headless_browser_context.h
@@ -106,6 +106,8 @@ class HEADLESS_EXPORT HeadlessBrowserContext::Builder {
   // By default |HeadlessBrowserContext| inherits the following options from
   // the browser instance. The methods below can be used to override these
   // settings. See HeadlessBrowser::Options for their meaning.
+  Builder& SetProductNameAndVersion(
+      const std::string& product_name_and_version);
   Builder& SetUserAgent(const std::string& user_agent);
   Builder& SetProxyServer(const net::HostPortPair& proxy_server);
   Builder& SetHostResolverRules(const std::string& host_resolver_rules);