PlzNavigate: Show error pages when the navigation failed before commit

content/browser/loader/navigation_url_loader_delegate.h

Index: content/browser/loader/navigation_url_loader_delegate.h
diff --git a/content/browser/loader/navigation_url_loader_delegate.h b/content/browser/loader/navigation_url_loader_delegate.h
index f558c754579a2541c2261ec47c6c89ffebf70c8c..62351aebf5fddcbc9c4ba4a07ab0cc4ace18c262 100644
--- a/content/browser/loader/navigation_url_loader_delegate.h
+++ b/content/browser/loader/navigation_url_loader_delegate.h
@@ -36,8 +36,9 @@ class CONTENT_EXPORT NavigationURLLoaderDelegate {
       scoped_ptr<StreamHandle> body_stream) = 0;
 
   // Called if the request fails before receving a response. |net_error| is a
-  // network error code for the failure.
-  virtual void OnRequestFailed(int net_error) = 0;
+  // network error code for the failure. |has_stale_copy_in_cache| is true if
+  // there is a stale copy of the unreachable page in cache.
+  virtual void OnRequestFailed(bool has_stale_copy_in_cache, int net_error) = 0;
 
   // Called after the network request has begun on the IO thread at time
   // |timestamp|. This is just a thread hop but is used to compare timing