Enable download page action for error page

chrome/common/render_messages.h

 // Copyright (c) 2012 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.
 
 // Multiply-included file, no traditional include guard.
 #include <stdint.h>
 #include <string>
 #include <vector>
 
 #include "base/files/file_path.h"
@@ skipping 323 matching lines @@
                     GURL /* Navigation correction service base URL */,
                     std::string /* language */,
                     std::string /* origin_country */,
                     std::string /* API key to use */,
                     GURL /* Google Search URL to use */)
 
 #if defined(OS_ANDROID)
 // Message sent from the renderer to the browser to schedule to download the
 // page at a later time.
 IPC_MESSAGE_ROUTED0(ChromeViewHostMsg_DownloadPageLater)
+
+// Message sent from the renderer to the browser to indicate if download button
+// is being shown in error page.
+IPC_MESSAGE_ROUTED1(ChromeViewHostMsg_SetIsShowingDownloadButtonInErrorPage,
+                    bool /* showing download button */)
 #endif  // defined(OS_ANDROID)
 
 //-----------------------------------------------------------------------------
 // Misc messages
 // These are messages sent from the renderer to the browser process.
 
 IPC_MESSAGE_CONTROL2(ChromeViewHostMsg_UpdatedCacheStats,
                      uint64_t /* capacity */,
                      uint64_t /* size */)
 
@@ skipping 229 matching lines @@
 // process so that they can be assigned to an Instant renderer.
 IPC_MESSAGE_CONTROL2(ChromeViewMsg_SetSearchURLs,
                      std::vector<GURL> /* search_urls */,
                      GURL /* new_tab_page_url */)
 
 #if BUILDFLAG(ENABLE_PLUGINS)
 // Sent by the renderer to check if crash reporting is enabled.
 IPC_SYNC_MESSAGE_CONTROL0_1(ChromeViewHostMsg_IsCrashReportingEnabled,
                             bool /* enabled */)
 #endif