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

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

Index: third_party/WebKit/Source/core/page/Page.cpp
diff --git a/third_party/WebKit/Source/core/page/Page.cpp b/third_party/WebKit/Source/core/page/Page.cpp
index 0fb749217d8d06e6504136175415ac9bfb220106..b50ea01041ec455c10b03e7af81fb8cdfc95eca5 100644
--- a/third_party/WebKit/Source/core/page/Page.cpp
+++ b/third_party/WebKit/Source/core/page/Page.cpp
@@ -63,13 +63,18 @@ 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) {
@@ -512,10 +517,13 @@ void Page::willCloseLayerTreeView(WebLayerTreeView& 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);
@@ -523,6 +531,7 @@ void Page::willBeDestroyed() {
   ASSERT(allPages().contains(this));
   allPages().remove(this);
   ordinaryPages().remove(this);
+  willBeClosedOrdinaryPages().remove(this);
 
   if (m_scrollingCoordinator)
     m_scrollingCoordinator->willBeDestroyed();