headless: Initial headless embedder API implementation

headless/public/headless_browser.cc

Index: headless/public/headless_browser.cc
diff --git a/headless/public/headless_browser.cc b/headless/public/headless_browser.cc
index cb8a855243a2a1314c7db517e502de2cd4491d57..4a7053669a5203c1063f9afebd42ff504decff99 100644
--- a/headless/public/headless_browser.cc
+++ b/headless/public/headless_browser.cc
@@ -2,7 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "content/public/common/user_agent.h"
 #include "headless/public/headless_browser.h"
+#include "net/url_request/url_request_context_getter.h"
 
 using Options = headless::HeadlessBrowser::Options;
 using Builder = headless::HeadlessBrowser::Options::Builder;
@@ -10,7 +12,11 @@ using Builder = headless::HeadlessBrowser::Options::Builder;
 namespace headless {
 
 Options::Options(int argc, const char** argv)
-    : argc(argc), argv(argv), devtools_http_port(kInvalidPort) {}
+    : argc(argc),
+      argv(argv),
+      user_agent(content::BuildUserAgentFromProduct("HeadlessChrome")),
+      devtools_http_port(kInvalidPort),
+      message_pump(nullptr) {}
 
 Options::~Options() {}
 
@@ -34,6 +40,11 @@ Builder& Builder::SetURLRequestContextGetter(
   return *this;
 }
 
+Builder& Builder::SetMessagePump(base::MessagePump* message_pump) {
+  options_.message_pump = message_pump;
+  return *this;
+}
+
 Options Builder::Build() {
   return options_;
 }