Bug 1426087: Decrement nsDocumentViewer::mDestroyRefCount in a separate function. r=jwatt

layout/base/nsDocumentViewer.cpp

@@ -1675,7 +1675,6 @@ 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;
   }
 
@@ -4472,6 +4471,12 @@ nsDocumentViewer::IncrementDestroyRefCount()
   ++mDestroyRefCount;
 }
 
+void
+nsDocumentViewer::DecrementDestroyRefCount()
+{
+  --mDestroyRefCount;
+}
+
 //------------------------------------------------------------
 
 #if defined(NS_PRINTING) && defined(NS_PRINT_PREVIEW)

layout/base/nsIDocumentViewerPrint.h

@@ -42,6 +42,7 @@ public:
   virtual mozilla::StyleSetHandle CreateStyleSet(nsIDocument* aDocument) = 0;
 
   virtual void IncrementDestroyRefCount() = 0;
+  virtual void DecrementDestroyRefCount() = 0;
 
   virtual void ReturnToGalleyPresentation() = 0;
 
@@ -76,6 +77,7 @@ NS_DEFINE_STATIC_IID_ACCESSOR(nsIDocumentViewerPrint,
   bool GetIsPrintPreview() override; \
   mozilla::StyleSetHandle CreateStyleSet(nsIDocument* aDocument) override; \
   void IncrementDestroyRefCount() override; \
+  void DecrementDestroyRefCount() override; \
   void ReturnToGalleyPresentation() override; \
   void OnDonePrinting() override; \
   bool IsInitializedForPrintPreview() override; \

layout/printing/nsPagePrintTimer.cpp

@@ -17,14 +17,8 @@ NS_IMPL_ISUPPORTS_INHERITED(nsPagePrintTimer, mozilla::Runnable, nsITimerCallbac
 
 nsPagePrintTimer::~nsPagePrintTimer()
 {
-  // "Destroy" the document viewer; this normally doesn't actually
-  // destroy it because of the IncrementDestroyRefCount call below
-  // XXX This is messy; the document viewer should use a single approach
-  // to keep itself alive during printing
-  nsCOMPtr<nsIContentViewer> cv(do_QueryInterface(mDocViewerPrint));
-  if (cv) {
-    cv->Destroy();
-  }
+  // This matches the IncrementDestroyRefCount call in the constructor.
+  mDocViewerPrint->DecrementDestroyRefCount();
 }
 
 nsresult