Finish completeSweep before shutting down V8

third_party/WebKit/Source/platform/heap/ThreadState.h

Index: third_party/WebKit/Source/platform/heap/ThreadState.h
diff --git a/third_party/WebKit/Source/platform/heap/ThreadState.h b/third_party/WebKit/Source/platform/heap/ThreadState.h
index ed066d6f421beffe4863ff7dc50d00fcfe2679e2..22a5856ba5ce2724f18c05faa298779f27fb36f6 100644
--- a/third_party/WebKit/Source/platform/heap/ThreadState.h
+++ b/third_party/WebKit/Source/platform/heap/ThreadState.h
@@ -190,6 +190,7 @@ public:
 
     static void attachMainThread();
     static void detachMainThread();
+    void cleanupMainThread();
 
     // Trace all persistent roots, called when marking the managed heap objects.
     static void visitPersistentRoots(Visitor*);
@@ -430,11 +431,6 @@ public:
         m_isolate = isolate;
         m_traceDOMWrappers = traceDOMWrappers;
     }
-    void unregisterTraceDOMWrappers()
-    {
-        m_isolate = nullptr;
-        m_traceDOMWrappers = nullptr;
-    }
 
     // By entering a gc-forbidden scope, conservative GCs will not
     // be allowed while handling an out-of-line allocation request.