Make sure pages that are closing but not yet closed are still suspended (non-preferred approach).

third_party/WebKit/Source/core/page/Page.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All
  * Rights Reserved.
  * Copyright (C) 2008 Torch Mobile Inc. All rights reserved.
  * (http://www.torchmobile.com/)
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 45 matching lines @@
 #include "platform/WebFrameScheduler.h"
 #include "platform/graphics/GraphicsLayer.h"
 #include "platform/plugins/PluginData.h"
 #include "public/platform/Platform.h"
 
 namespace blink {
 
 // Set of all live pages; includes internal Page objects that are
 // not observable from scripts.
 static Page::PageSet& allPages() {
-  DEFINE_STATIC_LOCAL(Page::PageSet, allPages, ());
-  return allPages;
+  DEFINE_STATIC_LOCAL(Page::PageSet, pages, ());
+  return pages;
 }
 
 Page::PageSet& Page::ordinaryPages() {
-  DEFINE_STATIC_LOCAL(Page::PageSet, ordinaryPages, ());
-  return ordinaryPages;
+  DEFINE_STATIC_LOCAL(Page::PageSet, pages, ());
+  return pages;
+}
+
+Page::PageSet& Page::willBeClosedOrdinaryPages() {
+  DEFINE_STATIC_LOCAL(Page::PageSet, pages, ());
+  return pages;
 }
 
 void Page::networkStateChanged(bool online) {
   HeapVector<Member<LocalFrame>> frames;
 
   // Get all the frames of all the pages in all the page groups
   for (Page* page : allPages()) {
     for (Frame* frame = page->mainFrame(); frame;
          frame = frame->tree().traverseNext()) {
       // FIXME: There is currently no way to dispatch events to out-of-process
@@ skipping 422 matching lines @@
   if (scrollingCoordinator())
     scrollingCoordinator()->layerTreeViewInitialized(layerTreeView);
 }
 
 void Page::willCloseLayerTreeView(WebLayerTreeView& layerTreeView) {
   if (m_scrollingCoordinator)
     m_scrollingCoordinator->willCloseLayerTreeView(layerTreeView);
 }
 
 void Page::willBeClosed() {
+  DCHECK(!ScopedPageSuspender::isActive());
   ordinaryPages().remove(this);
+  willBeClosedOrdinaryPages().add(this);
 }
 
 void Page::willBeDestroyed() {
+  DCHECK(!ScopedPageSuspender::isActive());
   Frame* mainFrame = m_mainFrame;
 
   mainFrame->detach(FrameDetachType::Remove);
 
   ASSERT(allPages().contains(this));
   allPages().remove(this);
   ordinaryPages().remove(this);
+  willBeClosedOrdinaryPages().remove(this);
 
   if (m_scrollingCoordinator)
     m_scrollingCoordinator->willBeDestroyed();
 
   chromeClient().chromeDestroyed();
   if (m_validationMessageClient)
     m_validationMessageClient->willBeDestroyed();
   m_mainFrame = nullptr;
 
   PageVisibilityNotifier::notifyContextDestroyed();
 }
 
 Page::PageClients::PageClients()
     : chromeClient(nullptr),
       contextMenuClient(nullptr),
       editorClient(nullptr),
       spellCheckerClient(nullptr) {}
 
 Page::PageClients::~PageClients() {}
 
 template class CORE_TEMPLATE_EXPORT Supplement<Page>;
 
 }  // namespace blink