Bug 1661137 - Decrement the document viewer's destroy blocker earlier. r=bobowen

Do it as soon as we're done printing, rather than waiting until the
print timer dies.

Differential Revision: https://phabricator.services.mozilla.com/D88569

layout/printing/nsPagePrintTimer.cpp

@@ -14,9 +14,16 @@ using namespace mozilla;
 NS_IMPL_ISUPPORTS_INHERITED(nsPagePrintTimer, mozilla::Runnable,
                             nsITimerCallback)
 
-nsPagePrintTimer::~nsPagePrintTimer() {
+nsPagePrintTimer::~nsPagePrintTimer() { Disconnect(); }
+
+void nsPagePrintTimer::Disconnect() {
+  mPrintJob = nullptr;
+  mPrintObj = nullptr;
+  if (mDocViewerPrint) {
     // This matches the IncrementDestroyBlockedCount call in the constructor.
     mDocViewerPrint->DecrementDestroyBlockedCount();
+    mDocViewerPrint = nullptr;
+  }
 }
 
 nsresult nsPagePrintTimer::StartTimer(bool aUseDelay) {

layout/printing/nsPagePrintTimer.h

@@ -30,7 +30,7 @@ class nsPagePrintTimer final : public mozilla::Runnable,
                    mozilla::dom::Document* aDocument, uint32_t aDelay)
       : Runnable("nsPagePrintTimer"),
         mPrintJob(aPrintJob),
-        mDocViewerPrint(*aDocViewerPrint),
+        mDocViewerPrint(aDocViewerPrint),
         mDocument(aDocument),
         mDelay(aDelay),
         mFiringCount(0),
@@ -52,10 +52,7 @@ class nsPagePrintTimer final : public mozilla::Runnable,
   void WaitForRemotePrint();
   void RemotePrintFinished();
 
-  void Disconnect() {
-    mPrintJob = nullptr;
-    mPrintObj = nullptr;
-  }
+  void Disconnect();
 
  private:
   ~nsPagePrintTimer();
@@ -66,7 +63,7 @@ class nsPagePrintTimer final : public mozilla::Runnable,
   void Fail();
 
   nsPrintJob* mPrintJob;
-  const mozilla::OwningNonNull<nsIDocumentViewerPrint> mDocViewerPrint;
+  nsCOMPtr<nsIDocumentViewerPrint> mDocViewerPrint;
   RefPtr<mozilla::dom::Document> mDocument;
   nsCOMPtr<nsITimer> mTimer;
   nsCOMPtr<nsITimer> mWatchDogTimer;

layout/printing/nsPrintJob.cpp

@@ -2556,9 +2556,8 @@ nsresult nsPrintJob::StartPagePrintTimer(const UniquePtr<nsPrintObject>& aPO) {
     nsCOMPtr<Document> doc = cv->GetDocument();
     NS_ENSURE_TRUE(doc, NS_ERROR_FAILURE);
 
-    RefPtr<nsPagePrintTimer> timer =
+    mPagePrintTimer =
         new nsPagePrintTimer(this, mDocViewerPrint, doc, printPageDelay);
-    timer.forget(&mPagePrintTimer);
 
     nsCOMPtr<nsIPrintSession> printSession;
     nsresult rv =