diff --git a/DEPS b/DEPS
index aa40e0434daadc..fef259df52e5fb 100644
--- a/DEPS
+++ b/DEPS
@@ -311,7 +311,7 @@ vars = {
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling V8
   # and whatever else without interference from each other.
-  'v8_revision': '1a0e6a82c5f5cb43513b781e027569896b60bcb4',
+  'v8_revision': '4902428d14d7b4244afbbdae1fbfdfa282eeb5b7',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling swarming_client
   # and whatever else without interference from each other.
diff --git a/REPLAY_BACKEND_REV b/REPLAY_BACKEND_REV
index 3417d08595c538..b99e57277ac5ac 100644
--- a/REPLAY_BACKEND_REV
+++ b/REPLAY_BACKEND_REV
@@ -1 +1 @@
-6c7e9991dcf557721c0566c2c0d68ac94f2a5b10
+8d5f91e301c3d248654f3158db03fd9098eca8bb
diff --git a/components/page_load_metrics/renderer/metrics_render_frame_observer.cc b/components/page_load_metrics/renderer/metrics_render_frame_observer.cc
index 9fd19f865d8e08..7d5bdd54bd8331 100644
--- a/components/page_load_metrics/renderer/metrics_render_frame_observer.cc
+++ b/components/page_load_metrics/renderer/metrics_render_frame_observer.cc
@@ -60,7 +60,6 @@ class MojoPageTimingSender : public PageTimingSender {
       const absl::optional<blink::MobileFriendliness>& mobile_friendliness,
       uint32_t soft_navigation_count) override {
     DCHECK(page_load_metrics_);
-    mojo::internal::AutoRecordReplayAssertBufferAllocations assertsEnabled("TT-366-1124");
     page_load_metrics_->UpdateTiming(
         limited_sending_mode_ ? CreatePageLoadTiming() : timing->Clone(),
         metadata->Clone(), new_features, std::move(resources),
diff --git a/third_party/blink/common/use_counter/use_counter_feature_tracker.cc b/third_party/blink/common/use_counter/use_counter_feature_tracker.cc
index 4b0450f1f44fef..26e2fee1aeeac5 100644
--- a/third_party/blink/common/use_counter/use_counter_feature_tracker.cc
+++ b/third_party/blink/common/use_counter/use_counter_feature_tracker.cc
@@ -35,10 +35,16 @@ bool UseCounterFeatureTracker::Test(const UseCounterFeature& feature) const {
 
 bool UseCounterFeatureTracker::TestAndSet(const UseCounterFeature& feature) {
   bool has_record = Test(feature);
-  REPLAY_ASSERT("[TT-366-1456] UseCounterFeatureTracker::TestAndSet %d %d %u",
-                has_record,
-                feature.type(),
-                feature.value());
+  REPLAY_ASSERT_IF(
+    // [Rebase-Check] This might change with a rebase.
+    // Ignore Cross-origin access check (WebFeature::kCrossOriginPropertyAccess)
+    // because it looks like an allowed divergence.
+    (int)feature.type() != 0 || ((int)feature.value() != 1977 && 
+      ((int)feature.value() < 4115 || (int)feature.value() > 4144)),
+    "[TT-366-1480] UseCounterFeatureTracker::TestAndSet %d %d %u",
+    has_record,
+    feature.type(),
+    feature.value());
   Set(feature, true);
   return has_record;
 }
diff --git a/third_party/blink/renderer/core/css/css_value.h b/third_party/blink/renderer/core/css/css_value.h
index 9fe46b30e12362..3247bd55f3de55 100644
--- a/third_party/blink/renderer/core/css/css_value.h
+++ b/third_party/blink/renderer/core/css/css_value.h
@@ -195,6 +195,8 @@ class CORE_EXPORT CSSValue : public GarbageCollected<CSSValue> {
   void TraceAfterDispatch(blink::Visitor* visitor) const {}
   void Trace(Visitor*) const;
 
+  uint8_t ReplayGetClassType() const { return class_type_; }
+
  protected:
   enum ClassType {
     kNumericLiteralClass,
diff --git a/third_party/blink/renderer/core/css/parser/css_parser_context.cc b/third_party/blink/renderer/core/css/parser/css_parser_context.cc
index afc03f4cf64ac8..8fcf453f472a6e 100644
--- a/third_party/blink/renderer/core/css/parser/css_parser_context.cc
+++ b/third_party/blink/renderer/core/css/parser/css_parser_context.cc
@@ -229,9 +229,6 @@ KURL CSSParserContext::CompleteURL(const String& url) const {
 }
 
 void CSSParserContext::Count(WebFeature feature) const {
-  REPLAY_ASSERT("[TT-366-1467] CSSParserContext::Count feat %d %d",
-                IsUseCounterRecordingEnabled(),
-                feature);
   if (IsUseCounterRecordingEnabled())
     document_->CountUse(feature);
 }
@@ -242,7 +239,7 @@ void CSSParserContext::CountDeprecation(WebFeature feature) const {
 }
 
 void CSSParserContext::Count(CSSParserMode mode, CSSPropertyID property) const {
-  REPLAY_ASSERT("[TT-366-1467] CSSParserContext::Count prop %d %d %d",
+  REPLAY_ASSERT_MAYBE_EVENTS_DISALLOWED("[TT-366-1480] CSSParserContext::Count prop %d %d %d",
                 IsUseCounterRecordingEnabled(),
                 (int)mode,
                 property);
diff --git a/third_party/blink/renderer/core/css/parser/css_parser_impl.cc b/third_party/blink/renderer/core/css/parser/css_parser_impl.cc
index 0e75c621c185e3..2a605f2afff897 100644
--- a/third_party/blink/renderer/core/css/parser/css_parser_impl.cc
+++ b/third_party/blink/renderer/core/css/parser/css_parser_impl.cc
@@ -662,6 +662,8 @@ StyleRuleBase* CSSParserImpl::ConsumeAtRule(CSSParserTokenStream& stream,
 StyleRuleBase* CSSParserImpl::ConsumeQualifiedRule(
     CSSParserTokenStream& stream,
     AllowedRulesType allowed_rules) {
+  REPLAY_ASSERT("[TT-366-1480] CSSParserImpl::ConsumeQualifiedRule %d",
+    allowed_rules);
   if (allowed_rules <= kRegularRules) {
     return ConsumeStyleRule(stream);
   }
diff --git a/third_party/blink/renderer/core/css/parser/css_selector_parser.cc b/third_party/blink/renderer/core/css/parser/css_selector_parser.cc
index ea2c004eaea9c3..8526c6a7aacff4 100644
--- a/third_party/blink/renderer/core/css/parser/css_selector_parser.cc
+++ b/third_party/blink/renderer/core/css/parser/css_selector_parser.cc
@@ -458,6 +458,9 @@ ArenaUniquePtr<CSSParserSelector> CSSSelectorParser::ConsumeRelativeSelector(
 ArenaUniquePtr<CSSParserSelector> CSSSelectorParser::ConsumeComplexSelector(
     CSSParserTokenRange& range) {
   ArenaUniquePtr<CSSParserSelector> selector = ConsumeCompoundSelector(range);
+  REPLAY_ASSERT("[TT-366-1480] CSSSelectorParser::ConsumeComplexSelector %u %d",
+    range.size(),
+    !!selector);
   if (!selector)
     return nullptr;
 
diff --git a/third_party/blink/renderer/core/css/resolver/font_builder.cc b/third_party/blink/renderer/core/css/resolver/font_builder.cc
index 59ff6a565c44a5..2b0ac6fba383e6 100644
--- a/third_party/blink/renderer/core/css/resolver/font_builder.cc
+++ b/third_party/blink/renderer/core/css/resolver/font_builder.cc
@@ -483,7 +483,7 @@ void FontBuilder::CreateFont(ComputedStyle& style,
                              const ComputedStyle* parent_style) {
   DCHECK(document_);
 
-  recordreplay::Assert("[RUN-1436-2237] FontBuilder::CreateFont A %u", flags_);
+  REPLAY_ASSERT("[TT-366-1480] FontBuilder::CreateFont A %u", flags_);
   if (!flags_)
     return;
 
@@ -496,7 +496,7 @@ void FontBuilder::CreateFont(ComputedStyle& style,
   FontSelector* font_selector = ComputeFontSelector(style);
   UpdateAdjustedSize(description, style, font_selector);
 
-  recordreplay::Assert("[RUN-1436-2237] FontBuilder::CreateFont B %d",
+  REPLAY_ASSERT("[TT-366-1480] FontBuilder::CreateFont B %d",
                        !!font_selector);
   style.SetFontInternal(Font(description, font_selector));
   flags_ = 0;
diff --git a/third_party/blink/renderer/core/css/resolver/match_result.cc b/third_party/blink/renderer/core/css/resolver/match_result.cc
index 67842b7b2ec297..dd1aca579f0670 100644
--- a/third_party/blink/renderer/core/css/resolver/match_result.cc
+++ b/third_party/blink/renderer/core/css/resolver/match_result.cc
@@ -68,19 +68,19 @@ void MatchResult::AddMatchedProperties(
 void MatchResult::FinishAddingUARules() {
   DCHECK_EQ(current_origin_, CascadeOrigin::kUserAgent);
   current_origin_ = CascadeOrigin::kUser;
-  REPLAY_ASSERT("[RUN-2424-3053] FinishAddingUARules");
+  REPLAY_ASSERT("[TT-366-1480] FinishAddingUARules");
 }
 
 void MatchResult::FinishAddingUserRules() {
   DCHECK_EQ(current_origin_, CascadeOrigin::kUser);
   current_origin_ = CascadeOrigin::kAuthorPresentationalHint;
-  REPLAY_ASSERT("[RUN-2424-3053] FinishAddingUserRules");
+  REPLAY_ASSERT("[TT-366-1480] FinishAddingUserRules");
 }
 
 void MatchResult::FinishAddingPresentationalHints() {
   DCHECK_EQ(current_origin_, CascadeOrigin::kAuthorPresentationalHint);
   current_origin_ = CascadeOrigin::kAuthor;
-  REPLAY_ASSERT("[RUN-2424-3053] FinishAddingPresentationalHints");
+  REPLAY_ASSERT("[TT-366-1480] FinishAddingPresentationalHints");
 }
 
 void MatchResult::FinishAddingAuthorRulesForTreeScope(
@@ -88,13 +88,14 @@ void MatchResult::FinishAddingAuthorRulesForTreeScope(
   DCHECK_EQ(current_origin_, CascadeOrigin::kAuthor);
   tree_scopes_.push_back(&tree_scope);
   current_tree_order_ = base::ClampAdd(current_tree_order_, 1);
-  REPLAY_ASSERT("[RUN-2424-3053] MatchResult::FinishAddingAuthorRulesForTreeScope %u",
+  REPLAY_ASSERT("[TT-366-1480] MatchResult::FinishAddingAuthorRulesForTreeScope %d %u",
+    tree_scope.RecordReplayId(),
     tree_scopes_.size()
   );
 }
 
 void MatchResult::Reset() {
-  REPLAY_ASSERT("[RUN-2424-3053] MatchResult::Reset %u",
+  REPLAY_ASSERT("[TT-366-1480] MatchResult::Reset %u",
     (unsigned)current_tree_order_
   );
 
diff --git a/third_party/blink/renderer/core/css/resolver/style_builder_converter.cc b/third_party/blink/renderer/core/css/resolver/style_builder_converter.cc
index c28f7f9189e711..5e4505aa3c223f 100644
--- a/third_party/blink/renderer/core/css/resolver/style_builder_converter.cc
+++ b/third_party/blink/renderer/core/css/resolver/style_builder_converter.cc
@@ -239,6 +239,8 @@ FontDescription::FamilyDescription StyleBuilderConverterBase::ConvertFontFamily(
     const CSSValue& value,
     FontBuilder* font_builder,
     const Document* document_for_count) {
+  REPLAY_ASSERT("[TT-366-1480] StyleBuilderConverterBase::ConvertFontFamily %s",
+    value.CssText().Utf8().c_str());
   FontDescription::FamilyDescription desc(FontDescription::kNoFamily);
 
   if (const auto* system_font =
diff --git a/third_party/blink/renderer/core/css/resolver/style_cascade.cc b/third_party/blink/renderer/core/css/resolver/style_cascade.cc
index 7bb37995e5a4f7..60e3cbee3562c7 100644
--- a/third_party/blink/renderer/core/css/resolver/style_cascade.cc
+++ b/third_party/blink/renderer/core/css/resolver/style_cascade.cc
@@ -172,6 +172,7 @@ void StyleCascade::AddInterpolations(const ActiveInterpolationsMap* map,
 }
 
 void StyleCascade::Apply(CascadeFilter filter) {
+  REPLAY_ASSERT("[TT-366-1480] StyleCascade::Apply %d", (int)generation_);
   AnalyzeIfNeeded();
 
   CascadeResolver resolver(filter, ++generation_);
@@ -637,6 +638,12 @@ void StyleCascade::LookupAndApply(const CSSProperty& property,
   DCHECK(!resolver.IsLocked(property));
 
   CascadePriority* priority = map_.Find(name);
+
+  REPLAY_ASSERT("[TT-366-1480] StyleCascade::LookupAndApply %d %d %d %d",
+    priority ? (int)priority->GetPosition() : -1,
+    priority ? (int)priority->GetGeneration() : -1,
+    priority ? (int)priority->GetOrigin() : -1,
+    name.Id());
   if (!priority)
     return;
 
@@ -660,6 +667,11 @@ void StyleCascade::LookupAndApplyValue(const CSSProperty& property,
 void StyleCascade::LookupAndApplyDeclaration(const CSSProperty& property,
                                              CascadePriority* priority,
                                              CascadeResolver& resolver) {
+  REPLAY_ASSERT("[TT-366-1480] StyleCascade::LookupAndApplyDeclaration %d %d %d",
+    property.PropertyID(),
+    (int)priority->GetGeneration(),
+    (int)resolver.generation_
+  );
   if (priority->GetGeneration() >= resolver.generation_) {
     // Already applied this generation.
     return;
@@ -787,6 +799,12 @@ const CSSValue* StyleCascade::Resolve(const CSSProperty& property,
 const CSSValue* StyleCascade::ResolveSubstitutions(const CSSProperty& property,
                                                    const CSSValue& value,
                                                    CascadeResolver& resolver) {
+  REPLAY_ASSERT("[TT-366-1480] StyleCascade::ResolveSubstitutions %d %d %d %d %d",
+    property.PropertyID(),
+    (int)value.ReplayGetClassType(),
+    !!DynamicTo<CSSCustomPropertyDeclaration>(value),
+    !!DynamicTo<CSSVariableReferenceValue>(value),
+    !!DynamicTo<cssvalue::CSSPendingSubstitutionValue>(value));
   if (const auto* v = DynamicTo<CSSCustomPropertyDeclaration>(value))
     return ResolveCustomProperty(property, *v, resolver);
   if (const auto* v = DynamicTo<CSSVariableReferenceValue>(value))
diff --git a/third_party/blink/renderer/core/css/resolver/style_resolver.cc b/third_party/blink/renderer/core/css/resolver/style_resolver.cc
index ba2f89d5566b74..fe80cd877bb5fe 100644
--- a/third_party/blink/renderer/core/css/resolver/style_resolver.cc
+++ b/third_party/blink/renderer/core/css/resolver/style_resolver.cc
@@ -1874,6 +1874,9 @@ StyleResolver::CacheSuccess StyleResolver::ApplyMatchedCache(
     const MatchResult& match_result) {
   const Element& element = state.GetElement();
 
+  REPLAY_ASSERT("[TT-366-1480] StyleResolver::ApplyMatchedCache %d",
+    element.RecordReplayId());
+
   MatchedPropertiesCache::Key key(match_result);
 
   bool is_inherited_cache_hit = false;
diff --git a/third_party/blink/renderer/core/css/resolver/style_resolver_state.cc b/third_party/blink/renderer/core/css/resolver/style_resolver_state.cc
index 662324f9634361..a8cff626d6b082 100644
--- a/third_party/blink/renderer/core/css/resolver/style_resolver_state.cc
+++ b/third_party/blink/renderer/core/css/resolver/style_resolver_state.cc
@@ -244,8 +244,8 @@ const CSSValue& StyleResolverState::ResolveLightDarkPair(
 }
 
 void StyleResolverState::UpdateFont() {
-  recordreplay::Assert("[RUN-1436-2226] StyleResolverState::UpdateFont %d",
-                       GetElement().RecordReplayId());
+  REPLAY_ASSERT("[TT-366-1480] StyleResolverState::UpdateFont %d",
+                GetElement().RecordReplayId());
   GetFontBuilder().CreateFont(StyleRef(), ParentStyle());
   SetConversionFontSizes(
       CSSToLengthConversionData::FontSizes(Style(), RootElementStyle()));
diff --git a/third_party/blink/renderer/core/dom/document.cc b/third_party/blink/renderer/core/dom/document.cc
index 8573622b41082b..4f33fe1ceeeb21 100644
--- a/third_party/blink/renderer/core/dom/document.cc
+++ b/third_party/blink/renderer/core/dom/document.cc
@@ -8749,9 +8749,6 @@ void Document::CountUse(mojom::WebFeature feature) const {
 }
 
 void Document::CountUse(mojom::WebFeature feature) {
-  REPLAY_ASSERT("[TT-366-1467] Document::CountUse %d %d",
-                !!execution_context_,
-                feature);
   if (execution_context_)
     execution_context_->CountUse(feature);
 }
@@ -8762,7 +8759,9 @@ void Document::CountDeprecation(mojom::WebFeature feature) {
 }
 
 void Document::CountProperty(CSSPropertyID property) const {
-  REPLAY_ASSERT("[TT-366-1467] Document::CountProperty %d %d",
+  REPLAY_ASSERT_MAYBE_EVENTS_DISALLOWED("[TT-366-1480] Document::CountProperty %d %d %d %d",
+                domWindow() ? domWindow()->RecordReplayId() : -1,
+                GetFrame() ? GetFrame()->RecordReplayId() : -1,
                 !!Loader(),
                 property);
   if (DocumentLoader* loader = Loader()) {
diff --git a/third_party/blink/renderer/core/dom/element.cc b/third_party/blink/renderer/core/dom/element.cc
index ad5b250eb75d4b..e68f4c7bc5637b 100644
--- a/third_party/blink/renderer/core/dom/element.cc
+++ b/third_party/blink/renderer/core/dom/element.cc
@@ -2294,6 +2294,11 @@ void Element::setAttribute(const QualifiedName& name,
 DISABLE_CFI_PERF
 void Element::AttributeChanged(const AttributeModificationParams& params) {
   const QualifiedName& name = params.name;
+  REPLAY_ASSERT("[TT-366-1480] Element::AttributeChanged %d %s=%s",
+    params.reason,
+    name.LocalName().Utf8().c_str(),
+    params.new_value.Utf8().c_str()
+  );
   if (name == html_names::kSlotAttr && params.old_value != params.new_value) {
     if (ShadowRoot* root = ShadowRootOfParent())
       root->DidChangeHostChildSlotName(params.old_value, params.new_value);
diff --git a/third_party/blink/renderer/core/frame/local_dom_window.cc b/third_party/blink/renderer/core/frame/local_dom_window.cc
index fc9ca164d1a230..362f0f12fedc8b 100644
--- a/third_party/blink/renderer/core/frame/local_dom_window.cc
+++ b/third_party/blink/renderer/core/frame/local_dom_window.cc
@@ -725,9 +725,6 @@ void LocalDOMWindow::AddInspectorIssue(AuditsIssue issue) {
 }
 
 void LocalDOMWindow::CountUse(mojom::WebFeature feature) {
-  REPLAY_ASSERT("[TT-366-1467] LocalDOMWindow::CountUse %d %d",
-                !!GetFrame(),
-                GetFrame() ? !!GetFrame()->Loader().GetDocumentLoader() : -1);
   if (!GetFrame())
     return;
   if (auto* loader = GetFrame()->Loader().GetDocumentLoader())
diff --git a/third_party/blink/renderer/core/frame/use_counter_impl.cc b/third_party/blink/renderer/core/frame/use_counter_impl.cc
index c08effa1500d0e..4b43485c9ff9c1 100644
--- a/third_party/blink/renderer/core/frame/use_counter_impl.cc
+++ b/third_party/blink/renderer/core/frame/use_counter_impl.cc
@@ -179,12 +179,6 @@ void UseCounterImpl::Count(const UseCounterFeature& feature,
   if (recordreplay::AreEventsDisallowed("UseCounterImpl::Count"))
     return;
 
-  REPLAY_ASSERT("[TT-366-1467] UseCounterImpl::Count %d %u %d %d",
-                !!source_frame,
-                mute_count_,
-                feature.type(),
-                feature.value());
-
   if (!source_frame)
     return;
 
diff --git a/third_party/blink/renderer/core/html/parser/html_tree_builder.cc b/third_party/blink/renderer/core/html/parser/html_tree_builder.cc
index e5aba55ee637ed..66d741fc4627ef 100644
--- a/third_party/blink/renderer/core/html/parser/html_tree_builder.cc
+++ b/third_party/blink/renderer/core/html/parser/html_tree_builder.cc
@@ -332,6 +332,10 @@ void HTMLTreeBuilder::ConstructTree(AtomicHTMLToken* token) {
   else
     ProcessToken(token);
 
+  REPLAY_ASSERT("[TT-366-1480] HTMLTreeBuilder::ConstructTree %d %d",
+    parser_->IsDetached(),
+    tree_.HasPendingTasks());
+
   if (parser_->IsDetached())
     return;
 
diff --git a/third_party/blink/renderer/platform/context_lifecycle_notifier.cc b/third_party/blink/renderer/platform/context_lifecycle_notifier.cc
index cea4e3c6bb1b18..d30e9a212e1dba 100644
--- a/third_party/blink/renderer/platform/context_lifecycle_notifier.cc
+++ b/third_party/blink/renderer/platform/context_lifecycle_notifier.cc
@@ -23,96 +23,26 @@ bool ContextLifecycleNotifier::IsContextDestroyed() const {
 void ContextLifecycleNotifier::AddContextLifecycleObserver(
     ContextLifecycleObserver* observer) {
   observers_.AddObserver(observer);
-
-  if (recordreplay::IsRecordingOrReplaying("values") && recordreplay::IsReplaying())
-    replay_observers_.push_back(observer);
 }
 
 void ContextLifecycleNotifier::RemoveContextLifecycleObserver(
     ContextLifecycleObserver* observer) {
   DCHECK(observers_.HasObserver(observer));
   observers_.RemoveObserver(observer);
-
-  for (wtf_size_t i = 0; i < replay_observers_.size(); i++) {
-    if (replay_observers_[i] == observer) {
-      replay_observers_.EraseAt(i);
-      break;
-    }
-  }
 }
 
 void ContextLifecycleNotifier::NotifyContextDestroyed() {
   context_destroyed_ = true;
 
   ScriptForbiddenScope forbid_script;
-  HeapVector<Member<ContextLifecycleObserver>> observers;
-  observers_.ForEachObserver([&](ContextLifecycleObserver* observer) {
-    observers.push_back(observer);
+  observers_.ForEachObserver([](ContextLifecycleObserver* observer) {
+    observer->NotifyContextDestroyed();
   });
   observers_.Clear();
-
-  std::sort(observers.begin(), observers.end(),
-            recordreplay::CompareMemberByPointerId<Member<ContextLifecycleObserver>>());
-
-  // When replaying, notify the same observers in the same order which were
-  // notified when recording. Because of the use of weak pointers in the
-  // HeapObserverSet the set contents can vary, so we manually record/replay
-  // the objects which should be notified. The replay_observers_ vector holds
-  // strong references on the observers when replaying so none of the observers
-  // we need to notify should already be collected.
-  if (recordreplay::IsRecordingOrReplaying("values", "ContextLifecycleNotifier::NotifyContextDestroyed") &&
-      recordreplay::FeatureEnabled("pointer-ids") &&
-      !recordreplay::AreEventsDisallowed()) {
-    size_t num_observers = recordreplay::RecordReplayValue("NotifyContextDestroyed NumObservers", observers.size());
-    int* observer_ids = new int[num_observers];
-
-    if (recordreplay::IsRecording()) {
-      for (wtf_size_t i = 0; i < observers.size(); i++) {
-        int id = recordreplay::PointerId(observers[i]);
-        CHECK(id);
-        observer_ids[i] = id;
-      }
-    }
-
-    recordreplay::RecordReplayBytes("ContextLifecycleNotifier::NotifyContextDestroyed ObserverIds",
-                                    observer_ids, num_observers * sizeof(int));
-
-    if (recordreplay::IsReplaying()) {
-      HeapVector<Member<ContextLifecycleObserver>> new_observers;
-      for (ContextLifecycleObserver* observer : observers) {
-        int id = recordreplay::PointerId(observer);
-        CHECK(id);
-        bool found = false;
-        for (wtf_size_t i = 0; i < num_observers; i++) {
-          if (observer_ids[i] == id) {
-            found = true;
-            break;
-          }
-        }
-        if (found)
-          new_observers.push_back(observer);
-      }
-
-      observers = std::move(new_observers);
-    }
-
-    delete[] observer_ids;
-  }
-
-  for (ContextLifecycleObserver* observer : observers) {
-    if (!recordreplay::AreEventsDisallowed()) {
-      recordreplay::Assert("ContextLifecycleNotifier::NotifyContextDestroyed #1 %d",
-                           recordreplay::PointerId(observer));
-    }
-    observer->NotifyContextDestroyed();
-  }
-
-  replay_observers_.clear();
 }
 
 void ContextLifecycleNotifier::Trace(Visitor* visitor) const {
   visitor->Trace(observers_);
-  visitor->Trace(replay_observers_);
 }
 
 }  // namespace blink
diff --git a/third_party/blink/renderer/platform/context_lifecycle_notifier.h b/third_party/blink/renderer/platform/context_lifecycle_notifier.h
index 4b08a750c293d3..8a22f89deb80a0 100644
--- a/third_party/blink/renderer/platform/context_lifecycle_notifier.h
+++ b/third_party/blink/renderer/platform/context_lifecycle_notifier.h
@@ -40,11 +40,6 @@ class PLATFORM_EXPORT ContextLifecycleNotifier : public GarbageCollectedMixin {
  private:
   HeapObserverSet<ContextLifecycleObserver> observers_;
   bool context_destroyed_ = false;
-
-  // When replaying, strong references are held on all observers, which are
-  // cleared out after the context is destroyed. This ensures we can notify
-  // the same observers when replaying as when originally recording
-  HeapVector<Member<ContextLifecycleObserver>> replay_observers_;
 };
 
 }  // namespace blink
diff --git a/third_party/blink/renderer/platform/heap_observer_set.h b/third_party/blink/renderer/platform/heap_observer_set.h
index 9a23d3be5df463..32df6b47730cbd 100644
--- a/third_party/blink/renderer/platform/heap_observer_set.h
+++ b/third_party/blink/renderer/platform/heap_observer_set.h
@@ -33,7 +33,12 @@ class PLATFORM_EXPORT HeapObserverSet {
   // Removes the given observer from this list. Does nothing if this observer is
   // not in this list.
   void RemoveObserver(ObserverType* observer) {
-    CHECK(iteration_state_ & kAllowingRemoval);
+    CHECK(iteration_state_ & kAllowingRemoval);    
+    if (recordreplay::AreEventsDisallowed() &&
+        recordreplay::IsRecordingOrReplaying("leak-references", "HeapObserverSet")) {
+      return;
+    }
+
     observers_.erase(observer);
     if (recordreplay::IsRecordingOrReplaying("avoid-weak-pointers",
                                              "HeapObserverSet"))
@@ -54,6 +59,11 @@ class PLATFORM_EXPORT HeapObserverSet {
   // Removes all the observers from this list.
   void Clear() {
     CHECK(iteration_state_ & kAllowingRemoval);
+    if (recordreplay::AreEventsDisallowed() &&
+        recordreplay::IsRecordingOrReplaying("leak-references", "HeapObserverSet")) {
+      return;
+    }
+
     observers_.clear();
     if (recordreplay::IsRecordingOrReplaying("avoid-weak-pointers",
                                              "HeapObserverSet"))