1 files changed, 12 insertions, 1 deletions
diff --git a/layout/base/nsDocumentViewer.cpp b/layout/base/nsDocumentViewer.cpp
index a1105ae52..137efb3cd 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) {
@@ -1611,7 +1617,6 @@ nsDocumentViewer::Destroy()
   // We also keep the viewer from being cached in session history, since
   // we require all documents there to be sanitized.
   if (mDestroyRefCount != 0) {
-    --mDestroyRefCount;
     return NS_OK;
   }
 
@@ -4420,6 +4425,12 @@ nsDocumentViewer::IncrementDestroyRefCount()
   ++mDestroyRefCount;
 }
 
+void
+nsDocumentViewer::DecrementDestroyRefCount()
+{
+  --mDestroyRefCount;
+}
+
 //------------------------------------------------------------
 
 #if defined(NS_PRINTING) && defined(NS_PRINT_PREVIEW)