Annotate ScriptWrappable-embedding singletons.

third_party/WebKit/Source/core/dom/MutationObserver.cpp

Index: third_party/WebKit/Source/core/dom/MutationObserver.cpp
diff --git a/third_party/WebKit/Source/core/dom/MutationObserver.cpp b/third_party/WebKit/Source/core/dom/MutationObserver.cpp
index 8b00d1453f80a749bc13e25cd7d1391a8f29d7f1..cc8ba513d31311142788631a61e3843ce27e41fd 100644
--- a/third_party/WebKit/Source/core/dom/MutationObserver.cpp
+++ b/third_party/WebKit/Source/core/dom/MutationObserver.cpp
@@ -167,6 +167,7 @@ void MutationObserver::observationEnded(
 }
 
 static MutationObserverSet& activeMutationObservers() {
+  ALLOW_UNSAFE_SINGLETON()
   DEFINE_STATIC_LOCAL(MutationObserverSet, activeObservers,
                       (new MutationObserverSet));
   return activeObservers;
@@ -178,11 +179,13 @@ using SlotChangeList = HeapVector<Member<HTMLSlotElement>>;
 // similar-origin browsing context.
 // https://html.spec.whatwg.org/multipage/browsers.html#unit-of-related-similar-origin-browsing-contexts
 static SlotChangeList& activeSlotChangeList() {
+  ALLOW_UNSAFE_SINGLETON()
   DEFINE_STATIC_LOCAL(SlotChangeList, slotChangeList, (new SlotChangeList));
   return slotChangeList;
 }
 
 static MutationObserverSet& suspendedMutationObservers() {
+  ALLOW_UNSAFE_SINGLETON()
   DEFINE_STATIC_LOCAL(MutationObserverSet, suspendedObservers,
                       (new MutationObserverSet));
   return suspendedObservers;