--- a/layout/printing/nsPrintData.cpp
+++ b/layout/printing/nsPrintData.cpp
@@ -19,17 +19,17 @@
 extern mozilla::LazyLogModule gPrintingLog;
 
 #define PR_PL(_p1) MOZ_LOG(gPrintingLog, mozilla::LogLevel::Debug, _p1);
 
 //---------------------------------------------------
 //-- nsPrintData Class Impl
 //---------------------------------------------------
 nsPrintData::nsPrintData(ePrintDataType aType)
-    : mType(aType), mPrintDocList(0), mOnStartSent(false), mIsAborted(false) {}
+    : mType(aType), mOnStartSent(false), mIsAborted(false) {}
 
 nsPrintData::~nsPrintData() {
   // Only Send an OnEndPrinting if we have started printing
   if (mOnStartSent && mType != eIsPrintPreview) {
     OnEndPrinting();
   }
 
   if (mPrintDC) {

--- a/layout/printing/nsPrintData.h
+++ b/layout/printing/nsPrintData.h
@@ -9,17 +9,16 @@
 
 #include "mozilla/Attributes.h"
 #include "mozilla/UniquePtr.h"
 
 // Interfaces
 #include "nsDeviceContext.h"
 #include "nsIPrintSettings.h"
 #include "nsISupportsImpl.h"
-#include "nsTArray.h"
 #include "nsCOMArray.h"
 
 class nsPrintObject;
 class nsIWebProgressListener;
 
 class nsPrintData {
  public:
   typedef enum { eIsPrinting, eIsPrintPreview } ePrintDataType;
@@ -43,21 +42,16 @@ class nsPrintData {
 
   nsCOMArray<nsIWebProgressListener> mPrintProgressListeners;
 
   // If there is a focused iframe, mSelectionRoot is set to its nsPrintObject.
   // Otherwise, if there is a selection, it is set to the root nsPrintObject.
   // Otherwise, it is unset.
   nsPrintObject* mSelectionRoot = nullptr;
 
-  // Array of non-owning pointers to all the nsPrintObjects owned by this
-  // nsPrintData. This includes this->mPrintObject, as well as all of its
-  // mKids (and their mKids, etc.)
-  nsTArray<nsPrintObject*> mPrintDocList;
-
   bool mOnStartSent;
   bool mIsAborted;  // tells us the document is being aborted
 
  private:
   nsPrintData() = delete;
   nsPrintData& operator=(const nsPrintData& aOther) = delete;
 
   ~nsPrintData();  // non-virtual

--- a/layout/printing/nsPrintJob.cpp
+++ b/layout/printing/nsPrintJob.cpp
@@ -129,33 +129,33 @@ static void DumpPrintObjectsListStart(co
                                       const nsTArray<nsPrintObject*>& aDocList);
 static void DumpPrintObjectsTree(nsPrintObject* aPO, int aLevel = 0,
                                  FILE* aFD = nullptr);
 static void DumpPrintObjectsTreeLayout(const UniquePtr<nsPrintObject>& aPO,
                                        nsDeviceContext* aDC, int aLevel = 0,
                                        FILE* aFD = nullptr);
 
 #  define DUMP_DOC_LIST(_title) \
-    DumpPrintObjectsListStart((_title), mPrt->mPrintDocList);
+    DumpPrintObjectsListStart((_title), mPrintDocList);
 #  define DUMP_DOC_TREE DumpPrintObjectsTree(mPrt->mPrintObject.get());
 #  define DUMP_DOC_TREELAYOUT \
     DumpPrintObjectsTreeLayout(mPrt->mPrintObject, mPrt->mPrintDC);
 #else
 #  define DUMP_DOC_LIST(_title)
 #  define DUMP_DOC_TREE
 #  define DUMP_DOC_TREELAYOUT
 #endif
 
 // -------------------------------------------------------
 // Helpers
 // -------------------------------------------------------
 
 /**
  * Build a tree of nsPrintObjects under aPO. It also appends a (depth first)
- * flat list of all the nsPrintObjects created to mPrt->mPrintDocList. If
+ * flat list of all the nsPrintObjects created to mPrintDocList. If
  * one of the nsPrintObject's document is the focused document, then the print
  * object is set as mPrt->mSelectionRoot.
  * @param aParentPO The parent nsPrintObject to populate, must not be null.
  */
 void nsPrintJob::BuildNestedPrintObjects(
     const UniquePtr<nsPrintObject>& aParentPO) {
   MOZ_ASSERT(aParentPO);
 
@@ -196,17 +196,17 @@ void nsPrintJob::BuildNestedPrintObjects
     }
 
     auto childPO = MakeUnique<nsPrintObject>();
     nsresult rv = childPO->InitAsNestedObject(docShell, doc, aParentPO.get());
     if (NS_FAILED(rv)) {
       MOZ_ASSERT_UNREACHABLE("Init failed?");
     }
 
-    mPrt->mPrintDocList.AppendElement(childPO.get());
+    mPrintDocList.AppendElement(childPO.get());
     BuildNestedPrintObjects(childPO);
     aParentPO->mKids.AppendElement(std::move(childPO));
   }
 }
 
 static nsresult GetDefaultPrintSettings(nsIPrintSettings** aSettings) {
   *aSettings = nullptr;
 
@@ -407,17 +407,17 @@ nsresult nsPrintJob::DoCommonPrint(bool 
 
   {
     nsAutoScriptBlocker scriptBlocker;
     printData->mPrintObject = MakeUnique<nsPrintObject>();
     rv = printData->mPrintObject->InitAsRootObject(docShell, aDoc,
                                                    mIsCreatingPrintPreview);
     NS_ENSURE_SUCCESS(rv, rv);
 
-    printData->mPrintDocList.AppendElement(printData->mPrintObject.get());
+    mPrintDocList.AppendElement(printData->mPrintObject.get());
 
     printData->mPrintObject->mFrameType = eDoc;
 
     BuildNestedPrintObjects(printData->mPrintObject);
   }
 
   // The nsAutoScriptBlocker above will now have been destroyed, which may
   // cause our print/print-preview operation to finish. In this case, we
@@ -694,20 +694,17 @@ nsresult nsPrintJob::ReconstructAndReflo
     gDumpLOFileNameCnt = 0;
   }
 #endif
 
   // In this loop, it's conceivable that one of our helpers might clear mPrt,
   // while we're using it & its members!  So we capture it in an owning local
   // reference & use that instead of using mPrt directly.
   RefPtr<nsPrintData> printData = mPrt;
-  for (uint32_t i = 0; i < printData->mPrintDocList.Length(); ++i) {
-    nsPrintObject* po = printData->mPrintDocList.ElementAt(i);
-    NS_ASSERTION(po, "nsPrintObject can't be null!");
-
+  for (nsPrintObject* po : mPrintDocList) {
     if (!po->PrintingIsEnabled() || po->mInvisible) {
       continue;
     }
 
     // When the print object has been marked as "print the document" (i.e,
     // po->PrintingIsEnabled() is true), mPresContext and mPresShell should be
     // non-nullptr (i.e., should've been created for the print) since they
     // are necessary to print the document.
@@ -736,17 +733,17 @@ nsresult nsPrintJob::ReconstructAndReflo
     // let's stop doing this printing.
     if (NS_WARN_IF(mPrt != printData)) {
       return NS_ERROR_FAILURE;
     }
 
     // For all views except the first one, setup the root view.
     // ??? Can there be multiple po for the top-level-document?
     bool documentIsTopLevel = true;
-    if (i != 0) {
+    if (po->mParent) {
       nsSize adjSize;
       bool doReturn;
       nsresult rv = SetRootView(po, doReturn, documentIsTopLevel, adjSize);
 
       MOZ_ASSERT(!documentIsTopLevel, "How could this happen?");
 
       if (NS_FAILED(rv) || doReturn) {
         return rv;
@@ -1440,21 +1437,18 @@ nsresult nsPrintJob::ReflowPrintObject(c
 
   return NS_OK;
 }
 
 //-------------------------------------------------------
 // Figure out how many documents and how many total pages we are printing
 void nsPrintJob::CalcNumPrintablePages(int32_t& aNumPages) {
   aNumPages = 0;
-  // Count the number of printable documents
-  // and printable pages
-  for (uint32_t i = 0; i < mPrt->mPrintDocList.Length(); i++) {
-    nsPrintObject* po = mPrt->mPrintDocList.ElementAt(i);
-    NS_ASSERTION(po, "nsPrintObject can't be null!");
+  // Count the number of printable documents and printable pages
+  for (nsPrintObject* po : mPrintDocList) {
     // Note: The po->mPresContext null-check below is necessary, because it's
     // possible po->mPresContext might never have been set.  (e.g., if
     // PrintingIsEnabled() returns false, ReflowPrintObject bails before setting
     // mPresContext)
     if (po->mPresContext && po->mPresContext->IsRootPaginatedDocument()) {
       nsPageSequenceFrame* seqFrame = po->mPresShell->GetPageSequenceFrame();
       if (seqFrame) {
         aNumPages += seqFrame->PrincipalChildList().GetLength();

--- a/layout/printing/nsPrintJob.h
+++ b/layout/printing/nsPrintJob.h
@@ -10,16 +10,17 @@
 #include "mozilla/layout/RemotePrintJobChild.h"
 #include "mozilla/UniquePtr.h"
 
 #include "nsCOMPtr.h"
 
 #include "nsHashKeys.h"
 #include "nsIFrame.h"  // For WeakFrame
 #include "nsSize.h"
+#include "nsTArray.h"
 #include "nsTHashtable.h"
 #include "nsWeakReference.h"
 
 // Interfaces
 #include "nsIWebProgress.h"
 #include "nsIWebProgressListener.h"
 
 // Classes
@@ -249,16 +250,21 @@ class nsPrintJob final : public nsIWebPr
   // member-data.
   RefPtr<nsPrintData> mPrt;
 
   RefPtr<nsPagePrintTimer> mPagePrintTimer;
 
   // Only set if this nsPrintJob was created for a real print.
   RefPtr<RemotePrintJobChild> mRemotePrintJob;
 
+  // Array of non-owning pointers to all the nsPrintObjects owned by this
+  // nsPrintJob. This includes mPrintObject, as well as all of its mKids (and
+  // their mKids, etc.)
+  nsTArray<nsPrintObject*> mPrintDocList;
+
   // If the code that initiates a print preview passes a PrintPreviewResolver
   // (a std::function) to be notified of the final sheet/page counts (once
   // we've sufficiently laid out the document to know what those are), that
   // callback is stored here.
   PrintPreviewResolver mPrintPreviewCallback;
 
   // The scale factor that would need to be applied to all pages to make the
   // widest page fit without overflowing/clipping.