Remove support for the keygen tag

content/common/render_process_messages.h

 // Copyright 2015 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.
 
 // Common IPC messages used for render processes.
 // Multiply-included message file, hence no include guard.
 
 #include <stdint.h>
 
 #include <string>
@@ skipping 20 matching lines @@
   IPC_STRUCT_TRAITS_MEMBER(font_point_size)
 IPC_STRUCT_TRAITS_END()
 #endif
 
 ////////////////////////////////////////////////////////////////////////////////
 // Messages sent from the browser to the render process.
 
 ////////////////////////////////////////////////////////////////////////////////
 // Messages sent from the render process to the browser.
 
-// Asks the browser process to generate a keypair for grabbing a client
-// certificate from a CA (<keygen> tag), and returns the signed public
-// key and challenge string.
-IPC_SYNC_MESSAGE_CONTROL4_1(RenderProcessHostMsg_Keygen,
-                            uint32_t /* key size index */,
-                            std::string /* challenge string */,
-                            GURL /* URL of requestor */,
-                            GURL /* Origin of top-level frame */,
-                            std::string /* signed public key and challenge */)
-
 // Message sent from the renderer to the browser to request that the browser
 // cache |data| associated with |url| and |expected_response_time|.
 IPC_MESSAGE_CONTROL3(RenderProcessHostMsg_DidGenerateCacheableMetadata,
                      GURL /* url */,
                      base::Time /* expected_response_time */,
                      std::vector<char> /* data */)
 
 // Message sent from the renderer to the browser to request that the browser
 // cache |data| for the specified CacheStorage entry.
 IPC_MESSAGE_CONTROL5(
@@ skipping 10 matching lines @@
                      bool /* enabled */)
 
 #if defined(OS_MACOSX)
 // Request that the browser load a font into shared memory for us.
 IPC_SYNC_MESSAGE_CONTROL1_3(RenderProcessHostMsg_LoadFont,
                             FontDescriptor /* font to load */,
                             uint32_t /* buffer size */,
                             base::SharedMemoryHandle /* font data */,
                             uint32_t /* font id */)
 #endif