DevTools: remove devtools_discovery (merged into content).

headless/lib/browser/headless_devtools_manager_delegate.cc

Index: headless/lib/browser/headless_devtools_manager_delegate.cc
diff --git a/headless/lib/browser/headless_devtools_manager_delegate.cc b/headless/lib/browser/headless_devtools_manager_delegate.cc
index adc2c5ef92ee1bd4a34dc58bf3c8cf08e72335a6..ce89824097031edb287f2b3faaad3e99253bcf50 100644
--- a/headless/lib/browser/headless_devtools_manager_delegate.cc
+++ b/headless/lib/browser/headless_devtools_manager_delegate.cc
@@ -72,6 +72,11 @@ std::string HeadlessDevToolsManagerDelegate::GetTargetTitle(
   return "";
 }
 
+scoped_refptr<content::DevToolsAgentHost>
+HeadlessDevToolsManagerDelegate::CreateNewTarget(const GURL& url) {
+  return nullptr;
+}
+
 std::unique_ptr<base::Value> HeadlessDevToolsManagerDelegate::CreateTarget(
     const base::DictionaryValue* params) {
   std::string url;