Lend LSan a hand and clear out singleton static persistents first.

third_party/WebKit/Source/platform/heap/PersistentNode.cpp

Index: third_party/WebKit/Source/platform/heap/PersistentNode.cpp
diff --git a/third_party/WebKit/Source/platform/heap/PersistentNode.cpp b/third_party/WebKit/Source/platform/heap/PersistentNode.cpp
index 3cb1821980c5530b49d00f6458b7c736b5d57df1..0e89f56e24e7c7bcc73932ac421f9630894827c4 100644
--- a/third_party/WebKit/Source/platform/heap/PersistentNode.cpp
+++ b/third_party/WebKit/Source/platform/heap/PersistentNode.cpp
@@ -57,20 +57,26 @@ void PersistentRegion::ensurePersistentNodeSlots(void* self,
 void PersistentRegion::releasePersistentNode(
     PersistentNode* persistentNode,
     ThreadState::PersistentClearCallback callback) {
-  ASSERT(!persistentNode->isUnused());
+  DCHECK(callback);
+  DCHECK(!persistentNode->isUnused());
   // 'self' is in use, containing the persistent wrapper object.
-  void* self = persistentNode->self();
-  if (callback) {
-    (*callback)(self);
-    ASSERT(persistentNode->isUnused());
-    return;
-  }
-  Persistent<DummyGCBase>* persistent =
-      reinterpret_cast<Persistent<DummyGCBase>*>(self);
-  persistent->clear();
-  ASSERT(persistentNode->isUnused());
+  (*callback)(persistentNode->self(), ThreadState::ReleasePersistent);
+  DCHECK(persistentNode->isUnused());
 }
 
+#if defined(LEAK_SANITIZER)
+void PersistentRegion::clearPersistentNode(
+    PersistentNode* persistentNode,
+    ThreadState::PersistentClearCallback callback) {
+  DCHECK(callback);
+  DCHECK(!persistentNode->isUnused());
+  // 'self' is in use, containing the persistent wrapper object.
+  (*callback)(persistentNode->self(), ThreadState::ClearPersistent);
+  // Cleared, not freed, so still usable.
+  DCHECK(!persistentNode->isUnused());
+}
+#endif
+
 // This function traces all PersistentNodes. If we encounter
 // a PersistentNodeSlot that contains only freed PersistentNodes,
 // we delete the PersistentNodeSlot. This function rebuilds the free