Remove support for the keygen tag

content/public/browser/content_browser_client.h

Index: content/public/browser/content_browser_client.h
diff --git a/content/public/browser/content_browser_client.h b/content/public/browser/content_browser_client.h
index 9d1756dec89cfc08ab87e015aae4ddf86b281c50..f00c2f8cc6be3546a84185c1396df3c9f6bbb5d5 100644
--- a/content/public/browser/content_browser_client.h
+++ b/content/public/browser/content_browser_client.h
@@ -381,9 +381,6 @@ class CONTENT_EXPORT ContentBrowserClient {
                                         ResourceContext* context);
 #endif  // BUILDFLAG(ENABLE_WEBRTC)
 
-  // Allow the embedder to control whether we can use <keygen>.
-  virtual bool AllowKeygen(const GURL& url, content::ResourceContext* context);
-
   // Allow the embedder to control whether we can use Web Bluetooth.
   // TODO(crbug.com/589228): Replace this with a use of the permission system.
   enum class AllowWebBluetoothResult {