From 23d67624cdebf5b25ed446ad52f6cd1cddebe34d Mon Sep 17 00:00:00 2001
From: cku <cku@mozilla.com>
Date: Mon, 18 Sep 2017 23:55:54 +0800
Subject: [PATCH] Bug 1401069 - Part 8. Give a detailed comment to explain how
 to react when hitting this assertion in OpenDocument(). r=fatseng

MozReview-Commit-ID: 74UkMV3ZOWm

--HG--
extra : rebase_source : 5fedf61f8a737ecac5668d372bff48b224859fdb
---
 widget/windows/PDFViaEMFPrintHelper.cpp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/widget/windows/PDFViaEMFPrintHelper.cpp b/widget/windows/PDFViaEMFPrintHelper.cpp
index 6721c544ce5e..de7a4ac756a9 100644
--- a/widget/windows/PDFViaEMFPrintHelper.cpp
+++ b/widget/windows/PDFViaEMFPrintHelper.cpp
@@ -37,8 +37,11 @@ nsresult
 PDFViaEMFPrintHelper::OpenDocument(nsIFile *aFile)
 {
   MOZ_ASSERT(aFile);
+
   if (mPDFDoc) {
-    MOZ_ASSERT_UNREACHABLE("We can only open one PDF at a time");
+    MOZ_ASSERT_UNREACHABLE("We can only open one PDF at a time,"
+                           "Use CloseDocument() to close the opened file"
+                           "before calling OpenDocument()");
     return NS_ERROR_FAILURE;
   }