Bug 1561079 - Run nsILoadURIDelegate::handleLoadError() even if we wouldn't show an error page r=smaug

Differential Revision: https://phabricator.services.mozilla.com/D36785

docshell/base/nsDocShell.cpp

@@ -4419,11 +4419,6 @@ nsDocShell::DisplayLoadError(nsresult aError, nsIURI* aURI,
     }
   }
 
-  // Test if the error should be displayed
-  if (!error) {
-    return NS_OK;
-  }
-
   if (mLoadURIDelegate) {
     nsCOMPtr<nsIURI> errorPageURI;
     rv = mLoadURIDelegate->HandleLoadError(aURI, aError,
@@ -4441,6 +4436,11 @@ nsDocShell::DisplayLoadError(nsresult aError, nsIURI* aURI,
     }
   }
 
+  // Test if the error should be displayed
+  if (!error) {
+    return NS_OK;
+  }
+
   if (!errorDescriptionID) {
     errorDescriptionID = error;
   }