diff --git a/layout/base/nsDocumentViewer.cpp b/layout/base/nsDocumentViewer.cpp
index 7f4d13977ab5..ca0b7569de17 100644
--- a/layout/base/nsDocumentViewer.cpp
+++ b/layout/base/nsDocumentViewer.cpp
@@ -714,6 +714,15 @@ nsDocumentViewer::Init(nsIWidget* aParentWidget,
 nsresult
 nsDocumentViewer::InitPresentationStuff(bool aDoInitialReflow)
 {
+  // We assert this because initializing the pres shell could otherwise cause
+  // re-entrancy into nsDocumentViewer methods, which might cause a different
+  // pres shell to be created.  Callers of InitPresentationStuff should ensure
+  // the call is appropriately bounded by an nsAutoScriptBlocker to decide
+  // when it is safe for these re-entrant calls to be made.
+  MOZ_ASSERT(!nsContentUtils::IsSafeToRunScript(),
+             "InitPresentationStuff must only be called when scripts are "
+             "blocked");
+
   if (GetIsPrintPreview())
     return NS_OK;
 
@@ -1773,6 +1782,10 @@ nsDocumentViewer::Destroy()
 
   // The document was not put in the bfcache
 
+  // Protect against pres shell destruction running scripts and re-entrantly
+  // creating a new presentation.
+  nsAutoScriptBlocker scriptBlocker;
+
   if (mPresShell) {
     DestroyPresShell();
   }
@@ -1940,6 +1953,10 @@ nsDocumentViewer::SetDocumentInternal(nsIDocument* aDocument,
 
   // Replace the current pres shell with a new shell for the new document
 
+  // Protect against pres shell destruction running scripts and re-entrantly
+  // creating a new presentation.
+  nsAutoScriptBlocker scriptBlocker;
+
   if (mPresShell) {
     DestroyPresShell();
   }
@@ -2145,7 +2162,17 @@ nsDocumentViewer::Show(void)
     }
   }
 
+  // Hold on to the document so we can use it after the script blocker below
+  // has been released (which might re-entrantly call into other
+  // nsDocumentViewer methods).
+  nsCOMPtr<nsIDocument> document = mDocument;
+
   if (mDocument && !mPresShell) {
+    // The InitPresentationStuff call below requires a script blocker, because
+    // its PresShell::Initialize call can cause scripts to run and therefore
+    // re-entrant calls to nsDocumentViewer methods to be made.
+    nsAutoScriptBlocker scriptBlocker;
+
     NS_ASSERTION(!mWindow, "Window already created but no presshell?");
 
     nsCOMPtr<nsIBaseWindow> base_win(mContainer);
@@ -2208,8 +2235,8 @@ nsDocumentViewer::Show(void)
   // Notify observers that a new page has been shown. This will get run
   // from the event loop after we actually draw the page.
   RefPtr<nsDocumentShownDispatcher> event =
-    new nsDocumentShownDispatcher(mDocument);
-  mDocument->Dispatch("nsDocumentShownDispatcher",
+    new nsDocumentShownDispatcher(document);
+  document->Dispatch("nsDocumentShownDispatcher",
                       TaskCategory::Other,
                       event.forget());
 
@@ -2253,24 +2280,23 @@ nsDocumentViewer::Hide(void)
     mPresShell->CaptureHistoryState(getter_AddRefs(layoutState));
   }
 
-  {
-    // Do not run ScriptRunners queued by DestroyPresShell() in the intermediate
-    // state before we're done destroying PresShell, PresContext, ViewManager, etc.
-    nsAutoScriptBlocker scriptBlocker;
-    DestroyPresShell();
+  // Do not run ScriptRunners queued by DestroyPresShell() in the intermediate
+  // state before we're done destroying PresShell, PresContext, ViewManager, etc.
+  nsAutoScriptBlocker scriptBlocker;
 
-    DestroyPresContext();
+  DestroyPresShell();
 
-    mViewManager   = nullptr;
-    mWindow        = nullptr;
-    mDeviceContext = nullptr;
-    mParentWidget  = nullptr;
+  DestroyPresContext();
 
-    nsCOMPtr<nsIBaseWindow> base_win(mContainer);
+  mViewManager   = nullptr;
+  mWindow        = nullptr;
+  mDeviceContext = nullptr;
+  mParentWidget  = nullptr;
 
-    if (base_win && !mAttachedToParent) {
-      base_win->SetParentWidget(nullptr);
-    }
+  nsCOMPtr<nsIBaseWindow> base_win(mContainer);
+
+  if (base_win && !mAttachedToParent) {
+    base_win->SetParentWidget(nullptr);
   }
 
   return NS_OK;
@@ -4510,6 +4536,10 @@ nsDocumentViewer::SetIsPrintPreview(bool aIsPrintPreview)
     mAutoBeforeAndAfterPrint = nullptr;
   }
 #endif
+
+  // Protect against pres shell destruction running scripts.
+  nsAutoScriptBlocker scriptBlocker;
+
   if (!aIsPrintPreview) {
     if (mPresShell) {
       DestroyPresShell();
@@ -4646,6 +4676,11 @@ NS_IMETHODIMP nsDocumentViewer::SetPageMode(bool aPageMode, nsIPrintSettings* aP
   // reftests that require a paginated context
   mIsPageMode = aPageMode;
 
+  // The DestroyPresShell call requires a script blocker, since the
+  // PresShell::Destroy call it does can cause scripts to run, which could
+  // re-entrantly call methods on the nsDocumentViewer.
+  nsAutoScriptBlocker scriptBlocker;
+
   if (mPresShell) {
     DestroyPresShell();
   }
@@ -4706,6 +4741,13 @@ nsDocumentViewer::SetIsHidden(bool aHidden)
 void
 nsDocumentViewer::DestroyPresShell()
 {
+  // We assert this because destroying the pres shell could otherwise cause
+  // re-entrancy into nsDocumentViewer methods, and all callers of
+  // DestroyPresShell need to do other cleanup work afterwards before it
+  // is safe for those re-entrant method calls to be made.
+  MOZ_ASSERT(!nsContentUtils::IsSafeToRunScript(),
+             "DestroyPresShell must only be called when scripts are blocked");
+
   nsIFrame* vmRootFrame =
     mViewManager && mViewManager->GetRootView()
       ? mViewManager->GetRootView()->GetFrame()
@@ -4720,7 +4762,6 @@ nsDocumentViewer::DestroyPresShell()
   if (selection && mSelectionListener)
     selection->RemoveSelectionListener(mSelectionListener);
 
-  nsAutoScriptBlocker scriptBlocker;
   bool hadRootFrame = !!mPresShell->GetRootFrame();
   mPresShell->Destroy();
   mPresShellDestroyed = true;
@@ -4761,6 +4802,10 @@ nsDocumentViewer::SetPrintPreviewPresentation(nsViewManager* aViewManager,
                                               nsPresContext* aPresContext,
                                               nsIPresShell* aPresShell)
 {
+  // Protect against pres shell destruction running scripts and re-entrantly
+  // creating a new presentation.
+  nsAutoScriptBlocker scriptBlocker;
+
   if (mPresShell) {
     DestroyPresShell();
   }