check whether the printing render frame host has been initialised before accepting a message in the…

headless/lib/browser/headless_print_manager.cc

 // Copyright 2017 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.
 
 #include "headless/lib/browser/headless_print_manager.h"
 
 #include <utility>
 #include <vector>
 
 #include "base/base64.h"
@@ skipping 155 matching lines @@
 
   auto print_params = base::MakeUnique<PrintMsg_PrintPages_Params>();
   RenderParamsFromPrintSettings(print_settings, &print_params->params);
   print_params->params.document_cookie = PrintSettings::NewCookie();
   return print_params;
 }
 
 bool HeadlessPrintManager::OnMessageReceived(
     const IPC::Message& message,
     content::RenderFrameHost* render_frame_host) {
+  if (!printing_rfh_) {
+    DLOG(WARNING)
+        << "Unexpected message received before GetPDFContents is called.";
+    render_frame_host->Send(new IPC::Message());

[jzfeng, 2017/05/18 08:12:47]

use DLOG(ERROR), and add the message type into the error message, so that we
know which IPC got wrong?

Could you only send an empty reply when the IPC type is
PrintHostMsg_GetDefaultPrintSettings, or PrintHostMsg_ScriptedPrint? Looks like
other messages don't need a reply.

+    return true;
+  }
+
   bool handled = true;
   IPC_BEGIN_MESSAGE_MAP(HeadlessPrintManager, message)
     IPC_MESSAGE_HANDLER(PrintHostMsg_ShowInvalidPrinterSettingsError,
                         OnShowInvalidPrinterSettingsError)
     IPC_MESSAGE_HANDLER(PrintHostMsg_DidPrintPage, OnDidPrintPage)
     IPC_MESSAGE_HANDLER_DELAY_REPLY(PrintHostMsg_GetDefaultPrintSettings,
                                     OnGetDefaultPrintSettings)
     IPC_MESSAGE_HANDLER_DELAY_REPLY(PrintHostMsg_ScriptedPrint, OnScriptedPrint)
     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
@@ skipping 44 matching lines @@
   if (!print_params_->pages.empty())
     number_pages_ = print_params_->pages.size();
 }
 
 void HeadlessPrintManager::OnDidPrintPage(
     const PrintHostMsg_DidPrintPage_Params& params) {
   if (!callback_) {
     DLOG(ERROR)
         << "Unexpected PrintHostMsg_DidPrintPage message from the renderer";
     return;
   }

[jzfeng, 2017/05/18 08:12:47]

remove this block since now it is checked in OnMessageReceived.

 
   const bool metafile_must_be_valid = expecting_first_page_;
   expecting_first_page_ = false;
 
   if (metafile_must_be_valid) {
     if (!base::SharedMemory::IsHandleValid(params.metafile_data_handle)) {
       ReleaseJob(INVALID_MEMORY_HANDLE);
       return;
     }
     auto shared_buf =
@@ skipping 45 matching lines @@
   if (result == PRINT_SUCCESS)
     callback_.Run(result, std::move(data_));
   else
     callback_.Run(result, std::string());
   printing_rfh_->Send(new PrintMsg_PrintingDone(printing_rfh_->GetRoutingID(),
                                                 result == PRINT_SUCCESS));
   Reset();
 }
 
 }  // namespace printing