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

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

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 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 42 matching lines @@
 class ContextMenuController;
 class Document;
 class DragCaretController;
 class DragController;
 class EditorClient;
 class FocusController;
 class Frame;
 class FrameHost;
 class PluginData;
 class PointerLockController;
+class ScopedPageSuspender;
 class ScrollingCoordinator;
 class Settings;
 class SpellCheckerClient;
 class ValidationMessageClient;
 class WebLayerTreeView;
 
 typedef uint64_t LinkHash;
 
 float deviceScaleFactor(LocalFrame*);
 
@@ skipping 107 matching lines @@
   Deprecation& deprecation() { return m_deprecation; }
   HostsUsingFeatures& hostsUsingFeatures() { return m_hostsUsingFeatures; }
 
   void setTabKeyCyclesThroughElements(bool b) {
     m_tabKeyCyclesThroughElements = b;
   }
   bool tabKeyCyclesThroughElements() const {
     return m_tabKeyCyclesThroughElements;
   }
 
-  // DefersLoading is used to delay loads during modal dialogs.
-  // Modal dialogs are supposed to freeze all background processes
-  // in the page, including prevent additional loads from staring/continuing.
-  void setSuspended(bool);
+  // Suspension is used to implement the "Optionally, pause while waiting for
+  // the user to acknowledge the message" step of simple dialog processing:
+  // https://html.spec.whatwg.org/multipage/webappapis.html#simple-dialogs
+  //
+  // Per https://html.spec.whatwg.org/multipage/webappapis.html#pause, no loads
+  // are allowed to start/continue in this state, and all background processing
+  // is also suspended.
   bool suspended() const { return m_suspended; }
 
   void setPageScaleFactor(float);
   float pageScaleFactor() const;
 
   float deviceScaleFactor() const { return m_deviceScaleFactor; }
   void setDeviceScaleFactor(float);
 
   static void allVisitedStateChanged(bool invalidateVisitedLinkHashes);
   static void visitedStateChanged(LinkHash visitedHash);
@@ skipping 17 matching lines @@
   static void networkStateChanged(bool online);
 
   DECLARE_TRACE();
 
   void layerTreeViewInitialized(WebLayerTreeView&);
   void willCloseLayerTreeView(WebLayerTreeView&);
 
   void willBeDestroyed();
 
  private:
+  friend class ScopedPageSuspender;
+
   explicit Page(PageClients&);
 
   void initGroup();
 
   // SettingsDelegate overrides.
   void settingsChanged(SettingsDelegate::ChangeType) override;
 
+  // ScopedPageSuspender helpers.
+  void setSuspended(bool);
+  static PageSet& willBeClosedOrdinaryPages();
+
   Member<PageAnimator> m_animator;
   const Member<AutoscrollController> m_autoscrollController;
   Member<ChromeClient> m_chromeClient;
   const Member<DragCaretController> m_dragCaretController;
   const Member<DragController> m_dragController;
   const Member<FocusController> m_focusController;
   const Member<ContextMenuController> m_contextMenuController;
   const Member<PointerLockController> m_pointerLockController;
   Member<ScrollingCoordinator> m_scrollingCoordinator;
 
@@ skipping 40 matching lines @@
   // Page.
   // FIXME: Most of the members of Page should move onto FrameHost.
   Member<FrameHost> m_frameHost;
 };
 
 extern template class CORE_EXTERN_TEMPLATE_EXPORT Supplement<Page>;
 
 }  // namespace blink
 
 #endif  // Page_h