Fix headless_browsertests failures with PlzNavigate.

content/browser/devtools/render_frame_devtools_agent_host.h

Index: content/browser/devtools/render_frame_devtools_agent_host.h
diff --git a/content/browser/devtools/render_frame_devtools_agent_host.h b/content/browser/devtools/render_frame_devtools_agent_host.h
index 74b482cf0d56a9248305774cc137c90b59d34508..76abb14b4742ad9e4164c5d203af8640d8318ba2 100644
--- a/content/browser/devtools/render_frame_devtools_agent_host.h
+++ b/content/browser/devtools/render_frame_devtools_agent_host.h
@@ -14,6 +14,7 @@
 #include "content/browser/devtools/devtools_agent_host_impl.h"
 #include "content/common/content_export.h"
 #include "content/public/browser/web_contents_observer.h"
+#include "net/base/net_errors.h"
 
 #if defined(OS_ANDROID)
 #include "ui/android/view_android.h"
@@ -49,6 +50,7 @@ class CONTENT_EXPORT RenderFrameDevToolsAgentHost
   static void OnBeforeNavigation(RenderFrameHost* current,
                                  RenderFrameHost* pending);
   static void OnBeforeNavigation(NavigationHandle* navigation_handle);
+  static void OnFailedNavigation(RenderFrameHost* host, net::Error error_code);
   static std::unique_ptr<NavigationThrottle> CreateThrottleForNavigation(
       NavigationHandle* navigation_handle);
   static bool IsNetworkHandlerEnabled(FrameTreeNode* frame_tree_node);
@@ -119,6 +121,7 @@ class CONTENT_EXPORT RenderFrameDevToolsAgentHost
   void AboutToNavigateRenderFrame(RenderFrameHost* old_host,
                                   RenderFrameHost* new_host);
   void AboutToNavigate(NavigationHandle* navigation_handle);
+  void OnFailedNavigation(net::Error error_code);
 
   void DispatchBufferedProtocolMessagesIfNecessary();