From 1e55a5d9188b87da8632e217b238838effb1cdeb Mon Sep 17 00:00:00 2001
From: wolfbeast <mcwerewolf@gmail.com>
Date: Wed, 7 Feb 2018 21:18:43 +0100
Subject: Bug 1261175.

---
 layout/base/nsDocumentViewer.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/layout/base/nsDocumentViewer.cpp b/layout/base/nsDocumentViewer.cpp
index a1105ae52..782ac332c 100644
--- a/layout/base/nsDocumentViewer.cpp
+++ b/layout/base/nsDocumentViewer.cpp
@@ -544,6 +544,12 @@ nsDocumentViewer::~nsDocumentViewer()
     mDocument->Destroy();
   }
 
+  if (mPrintEngine) {
+    mPrintEngine->Destroy();
+    mPrintEngine = nullptr;
+  }
+
+  MOZ_RELEASE_ASSERT(mDestroyRefCount == 0);
   NS_ASSERTION(!mPresShell && !mPresContext,
                "User did not call nsIContentViewer::Destroy");
   if (mPresShell || mPresContext) {
-- 
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