Bug 1769717 - Remove nsPrintJob::GetPrintPreviewPresShell(). r=emilio

Long ago we used to play switcheroo with PresShells in order to print a
document, but for over a decade we've been cloning the document that is
to be printed (bug 487667). Since then we've had no need for this method.

Differential Revision: https://phabricator.services.mozilla.com/D146545

layout/base/nsDocumentViewer.cpp

@@ -3019,8 +3019,7 @@ nsDocumentViewer::PrintPreviewScrollToPage(int16_t aType, int32_t aPageNum) {
   if (!GetIsPrintPreview() || mPrintJob->GetIsCreatingPrintPreview())
     return NS_ERROR_FAILURE;
 
-  nsIScrollableFrame* sf =
-      mPrintJob->GetPrintPreviewPresShell()->GetRootScrollFrameAsScrollable();
+  nsIScrollableFrame* sf = mPresShell->GetRootScrollFrameAsScrollable();
   if (!sf) return NS_OK;
 
   auto [seqFrame, sheetCount] = mPrintJob->GetSeqFrameAndCountSheets();
@@ -3094,8 +3093,7 @@ nsDocumentViewer::GetCurrentSheetFrameAndNumber() const {
     return {nullptr, 0};
   }
 
-  nsIScrollableFrame* sf =
-      mPrintJob->GetPrintPreviewPresShell()->GetRootScrollFrameAsScrollable();
+  nsIScrollableFrame* sf = mPresShell->GetRootScrollFrameAsScrollable();
   if (!sf) {
     // No scrollable contents, returns 1 even if there are multiple sheets.
     return {seqFrame->PrincipalChildList().FirstChild(), 1};

layout/printing/nsPrintJob.cpp

@@ -276,10 +276,6 @@ bool nsPrintJob::CheckBeforeDestroy() const {
   return mPrt && mPrt->mPreparingForPrint;
 }
 
-PresShell* nsPrintJob::GetPrintPreviewPresShell() {
-  return mPrtPreview->mPrintObject->mPresShell;
-}
-
 //-------------------------------------------------------
 void nsPrintJob::Destroy() {
   if (mIsDestroying) {

layout/printing/nsPrintJob.h

@@ -150,7 +150,6 @@ class nsPrintJob final : public nsIWebProgressListener,
   void FirePrintingErrorEvent(nsresult aPrintError);
 
   bool CheckBeforeDestroy() const;
-  mozilla::PresShell* GetPrintPreviewPresShell();
   nsresult Cancel();
   void Destroy();
   void DestroyPrintingData();