Remove performanceMonitor()->unsubscribeAll() from Performance's destructor

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 86 matching lines @@
     return 0.0;
 
   return loader->timing().referenceMonotonicTime();
 }
 
 Performance::Performance(LocalFrame* frame)
     : PerformanceBase(toTimeOrigin(frame)),
       ContextLifecycleObserver(frame ? frame->document() : nullptr) {}
 
 Performance::~Performance() {
-  if (frame())
-    frame()->performanceMonitor()->unsubscribeAll(this);
+  // contextDestryoed() should have been called and the performance
+  // monitors should have been unsubscribed.
+  DCHECK(!frame());
 }
 
 void Performance::contextDestroyed() {
   frame()->performanceMonitor()->unsubscribeAll(this);
 }
 
 ExecutionContext* Performance::getExecutionContext() const {
   if (!frame())
     return nullptr;
   return frame()->document();
@@ skipping 121 matching lines @@
     HTMLFrameOwnerElement* frameOwner =
         culpritDomWindow->document()->localOwner();
     addLongTaskTiming(startTime, endTime, attribution.first,
                       getFrameAttribute(frameOwner, HTMLNames::srcAttr, false),
                       getFrameAttribute(frameOwner, HTMLNames::idAttr, false),
                       getFrameAttribute(frameOwner, HTMLNames::nameAttr, true));
   }
 }
 
 }  // namespace blink