Oilpan: support observer retirement during lifetime notifications.

Source/core/page/PageLifecycleNotifier.cpp

Index: Source/core/page/PageLifecycleNotifier.cpp
diff --git a/Source/core/page/PageLifecycleNotifier.cpp b/Source/core/page/PageLifecycleNotifier.cpp
index 2a6f3869481dc57f8840bc785acf5f467f7ead2a..bffda9050ecfd0c5264725a605a2bad46d0fb014 100644
--- a/Source/core/page/PageLifecycleNotifier.cpp
+++ b/Source/core/page/PageLifecycleNotifier.cpp
@@ -34,15 +34,43 @@ namespace blink {
 void PageLifecycleNotifier::notifyPageVisibilityChanged()
 {
     TemporaryChange<IterationType> scope(m_iterating, IteratingOverAll);
+#if !ENABLE(OILPAN)
+    // Notifications perform unknown amounts of heap allocations,
+    // which might trigger (conservative) GCs. This will flush out
+    // dead observers, causing the _non-heap_ set be updated. Snapshot
+    // the observers and explicitly check if they're still alive before
+    // notifying.
+    Vector<RawPtr<PageLifecycleObserver>> snapshotOfObservers;
+    copyToVector(m_observers, snapshotOfObservers);
+    for (PageLifecycleObserver* observer : snapshotOfObservers) {
+        if (m_observers.contains(observer))
+            observer->pageVisibilityChanged();
+    }
+#else
     for (PageLifecycleObserver* observer : m_observers)
         observer->pageVisibilityChanged();
+#endif
 }
 
 void PageLifecycleNotifier::notifyDidCommitLoad(LocalFrame* frame)
 {
     TemporaryChange<IterationType> scope(m_iterating, IteratingOverAll);
+#if !ENABLE(OILPAN)
+    // Notifications perform unknown amounts of heap allocations,
+    // which might trigger (conservative) GCs. This will flush out
+    // dead observers, causing the _non-heap_ set be updated. Snapshot
+    // the observers and explicitly check if they're still alive before
+    // notifying.
+    Vector<RawPtr<PageLifecycleObserver>> snapshotOfObservers;
+    copyToVector(m_observers, snapshotOfObservers);
+    for (PageLifecycleObserver* observer : snapshotOfObservers) {
+        if (m_observers.contains(observer))
+            observer->didCommitLoad(frame);
+    }
+#else
     for (PageLifecycleObserver* observer : m_observers)
         observer->didCommitLoad(frame);
+#endif
 }
 
 } // namespace blink