Bug 1486968. Remove nsPrintJob::mOldPrtPreview. r=bobowen

Differential Revision: https://phabricator.services.mozilla.com/D56205

--HG--
extra : moz-landing-system : lando

layout/printing/nsPrintJob.cpp

@@ -574,7 +574,6 @@ void nsPrintJob::Destroy() {
 
 #ifdef NS_PRINT_PREVIEW
   mPrtPreview = nullptr;
-  mOldPrtPreview = nullptr;
 #endif
   mDocViewerPrint = nullptr;
 }
@@ -748,10 +747,6 @@ nsresult nsPrintJob::DoCommonPrint(bool aIsPrintPreview,
     nsCOMPtr<nsIPrintingPromptService> pps(
         do_QueryInterface(aWebProgressListener));
     mProgressDialogIsShown = pps != nullptr;
-
-    if (mIsDoingPrintPreview) {
-      mOldPrtPreview = std::move(mPrtPreview);
-    }
   } else {
     mProgressDialogIsShown = false;
   }
@@ -776,6 +771,11 @@ nsresult nsPrintJob::DoCommonPrint(bool aIsPrintPreview,
   printData->mPrintSettings->GetShrinkToFit(&printData->mShrinkToFit);
 
   if (aIsPrintPreview) {
+    // Our new print preview nsPrintData is stored in mPtr until we move it
+    // to mPrtPreview once we've finish creating the print preview. We must
+    // clear mPtrPreview so that code will use mPtr until that happens.
+    mPrtPreview = nullptr;
+
     mIsCreatingPrintPreview = true;
     SetIsPrintPreview(true);
     nsCOMPtr<nsIContentViewer> viewer = do_QueryInterface(mDocViewerPrint);
@@ -2993,10 +2993,6 @@ nsresult nsPrintJob::FinishPrintPreview() {
   // At this point we are done preparing everything
   // before it is to be created
 
-  if (mIsDoingPrintPreview && mOldPrtPreview) {
-    mOldPrtPreview = nullptr;
-  }
-
   printData->OnEndPrinting();
   // XXX If mPrt becomes nullptr or different instance here, what should we
   //     do?

layout/printing/nsPrintJob.h

@@ -273,9 +273,11 @@ class nsPrintJob final : public nsIObserver,
   // member-data.
   RefPtr<nsPrintData> mPrt;
 
-  // Print Preview
+  // The nsPrintData for our last print preview (replaced every time the
+  // user changes settings in the print preview window).
+  // Note: Our new print preview nsPrintData is stored in mPtr until we move it
+  // to mPrtPreview once we've finish creating the print preview.
   RefPtr<nsPrintData> mPrtPreview;
-  RefPtr<nsPrintData> mOldPrtPreview;
 
   nsPagePrintTimer* mPagePrintTimer = nullptr;