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

headless/lib/browser/headless_print_manager.cc

Index: headless/lib/browser/headless_print_manager.cc
diff --git a/headless/lib/browser/headless_print_manager.cc b/headless/lib/browser/headless_print_manager.cc
index 036c7471fcdc7cee8c35a46ad69b0121eb12c853..6e6efe40b460da151e579fe300cc2efc8e198f1c 100644
--- a/headless/lib/browser/headless_print_manager.cc
+++ b/headless/lib/browser/headless_print_manager.cc
@@ -173,6 +173,25 @@ HeadlessPrintManager::GetPrintParamsFromSettings(
 bool HeadlessPrintManager::OnMessageReceived(
     const IPC::Message& message,
     content::RenderFrameHost* render_frame_host) {
+  if (!printing_rfh_ &&
+      (message.type() == PrintHostMsg_GetDefaultPrintSettings::ID ||
+       message.type() == PrintHostMsg_ScriptedPrint::ID)) {

[jzfeng, 2017/05/19 01:01:08]

nit: check for PrintHostMsg_DidPrintPage here?
Or you can leave the check in OnDidPrintPage as is.

+    std::string type;
+    switch (message.type()) {
+      case PrintHostMsg_GetDefaultPrintSettings::ID:
+        type = "GetDefaultPrintSettings";
+        break;
+      case PrintHostMsg_ScriptedPrint::ID:
+        type = "ScriptedPrint";
+        break;

[Sami, 2017/05/19 13:10:01]

Please add a default case too.

+    }
+    DLOG(ERROR)
+        << "Unexpected message received before GetPDFContents is called: "
+        << type;
+    render_frame_host->Send(new IPC::Message());

[Sami, 2017/05/19 13:10:01]

Does this end up dropping the print request on the floor or what happens? I
guess ideally we'd tell the embedder about it somehow? Maybe add a TODO to that
effect?

+    return true;
+  }
+
   bool handled = true;
   IPC_BEGIN_MESSAGE_MAP(HeadlessPrintManager, message)
     IPC_MESSAGE_HANDLER(PrintHostMsg_ShowInvalidPrinterSettingsError,
@@ -233,12 +252,6 @@ void HeadlessPrintManager::OnDidGetPrintedPagesCount(int cookie,
 
 void HeadlessPrintManager::OnDidPrintPage(
     const PrintHostMsg_DidPrintPage_Params& params) {
-  if (!callback_) {
-    DLOG(ERROR)
-        << "Unexpected PrintHostMsg_DidPrintPage message from the renderer";
-    return;
-  }
-
   const bool metafile_must_be_valid = expecting_first_page_;
   expecting_first_page_ = false;