Bug 1557687. Remove nsPrintData::mDocWasToBeDestroyed. r=bobowen

This shows that this variable has never been read going back all the way to
the original Mercurial import in 2007:

  hg grep -f --diff mDocWasToBeDestroyed layout/printing/ns*

Differential Revision: https://phabricator.services.mozilla.com/D34143

--HG--
extra : rebase_source : c14a51dab1825e26fb8031d291d2c69e78931c84
extra : amend_source : 73794b07d703987db8d2eb49dd97d74b1a9be325

layout/printing/nsPrintData.cpp

@@ -33,7 +33,6 @@ nsPrintData::nsPrintData(ePrintDataType aType)
       mOnStartSent(false),
       mIsAborted(false),
       mPreparingForPrint(false),
-      mDocWasToBeDestroyed(false),
       mShrinkToFit(false),
       mNumPrintablePages(0),
       mNumPagesPrinted(0),

layout/printing/nsPrintData.h

@@ -31,13 +31,6 @@ class PrintPreviewUserEventSuppressor;
 // mPreparingForPrint - indicates that we have started Printing but
 //   have not gone to the timer to start printing the pages. It gets turned
 //   off right before we go to the timer.
-//
-// mDocWasToBeDestroyed - Gets set when "someone" tries to unload the document
-//   while we were prparing to Print. This typically happens if a user starts
-//   to print while a page is still loading. If they start printing and pause
-//   at the print dialog and then the page comes in, we then abort printing
-//   because the document is no longer stable.
-//
 //------------------------------------------------------------------------
 class nsPrintData {
   typedef mozilla::PrintPreviewUserEventSuppressor
@@ -79,7 +72,6 @@ class nsPrintData {
   bool mOnStartSent;
   bool mIsAborted;          // tells us the document is being aborted
   bool mPreparingForPrint;  // see comments above
-  bool mDocWasToBeDestroyed;  // see comments above
   bool mShrinkToFit;
   int32_t mNumPrintablePages;
   int32_t mNumPagesPrinted;

layout/printing/nsPrintJob.cpp

@@ -630,15 +630,6 @@ nsresult nsPrintJob::Initialize(nsIDocumentViewerPrint* aDocViewerPrint,
   return NS_OK;
 }
 
-//-------------------------------------------------------
-bool nsPrintJob::CheckBeforeDestroy() {
-  if (mPrt && mPrt->mPreparingForPrint) {
-    mPrt->mDocWasToBeDestroyed = true;
-    return true;
-  }
-  return false;
-}
-
 //-------------------------------------------------------
 nsresult nsPrintJob::Cancel() {
   if (mPrt && mPrt->mPrintSettings) {

layout/printing/nsPrintJob.h

@@ -208,7 +208,8 @@ class nsPrintJob final : public nsIObserver,
                              nsAString& aTitle, nsAString& aURLStr,
                              eDocTitleDefault aDefType);
 
-  bool CheckBeforeDestroy();
+  bool CheckBeforeDestroy() const { return mPrt && mPrt->mPreparingForPrint; }
+
   nsresult Cancel();
 
   mozilla::PresShell* GetPrintPreviewPresShell() {