PlzNavigate: Show error pages when the navigation failed before commit

content/browser/frame_host/navigator.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_FRAME_HOST_NAVIGATOR_H_
 #define CONTENT_BROWSER_FRAME_HOST_NAVIGATOR_H_
 
 #include "base/memory/ref_counted.h"
 #include "base/time/time.h"
 #include "content/common/content_export.h"
@@ skipping 125 matching lines @@
       scoped_refptr<ResourceRequestBody> body);
 
   // PlzNavigate
   // Signal |render_frame_host| that a navigation is ready to commit (the
   // response to the navigation request has been received).
   virtual void CommitNavigation(FrameTreeNode* frame_tree_node,
                                 ResourceResponse* response,
                                 scoped_ptr<StreamHandle> body);
 
   // PlzNavigate
+  // Called when a NavigationRequest for |frame_tree_node| failed. An
+  // appropriate RenderFrameHost should be selected and asked to show an error
+  // page.

[Charlie Reis, 2015/04/09 00:07:30]

Please add what has_stale_copy_in_cache means.  Is there a copy of the page in
the cache?  Of the error page?  Why does it matter?

[clamy, 2015/04/10 14:04:49]

Done. This is needed by the WebURLError, which is used by embedders of content.

+  virtual void FailedNavigation(FrameTreeNode* frame_tree_node,
+                                bool has_stale_copy_in_cache,
+                                int error_code) {}
+
+  // PlzNavigate
   // Cancel a NavigationRequest for |frame_tree_node|. Called when
   // |frame_tree_node| is destroyed.
   virtual void CancelNavigation(FrameTreeNode* frame_tree_node) {}
 
   // Called when the network stack started handling the navigation request
   // so that the |timestamp| when it happened can be recorded into an histogram.
   // The |url| is used to verify we're tracking the correct navigation.
   // TODO(carlosk): once PlzNavigate is the only navigation implementation
   // remove the URL parameter and rename this method to better suit its naming
   // conventions.
@@ skipping 12 matching lines @@
   virtual bool IsWaitingForBeforeUnloadACK(FrameTreeNode* frame_tree_node);
 
  protected:
   friend class base::RefCounted<Navigator>;
   virtual ~Navigator() {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_FRAME_HOST_NAVIGATOR_H_