Fix vcall on nullptr in ~Performance.

third_party/WebKit/Source/core/timing/Performance.cpp

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  * Copyright (C) 2012 Intel Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 45 matching lines @@
 
   return loader->timing().referenceMonotonicTime();
 }
 
 Performance::Performance(LocalFrame* frame)
     : PerformanceBase(toTimeOrigin(frame)),
       DOMWindowProperty(frame),
       m_observingLongTasks(false) {}
 
 Performance::~Performance() {
+  if (!frame()) {
+    return;
+  }
   LocalFrame* localRoot = frame()->localFrameRoot();
   if (m_observingLongTasks && localRoot) {
     m_observingLongTasks = false;
     localRoot->disableInspectorWebPerfAgent(this);
   }
 }
 
 ExecutionContext* Performance::getExecutionContext() const {
   if (!frame())
     return nullptr;
@@ skipping 48 matching lines @@
 }
 
 DEFINE_TRACE(Performance) {
   visitor->trace(m_navigation);
   visitor->trace(m_timing);
   DOMWindowProperty::trace(visitor);
   PerformanceBase::trace(visitor);
 }
 
 }  // namespace blink