Assert event timestamp to be monotonic and not from future

third_party/WebKit/Source/platform/PlatformEvent.h

 /*
  * Copyright (C) 2011 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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 #ifndef PlatformEvent_h
 #define PlatformEvent_h
 
 #include "wtf/Allocator.h"
+#include "wtf/CurrentTime.h"
 #include "wtf/Noncopyable.h"
 
 namespace blink {
 
 class PlatformEvent {
     DISALLOW_NEW();
 public:
     enum EventType {
         NoType = 0,
 
@@ skipping 112 matching lines @@
         , m_modifiers(0)
         , m_timestamp(0)
     {
     }
 
     PlatformEvent(EventType type, Modifiers modifiers, double timestamp)
         : m_type(type)
         , m_modifiers(modifiers)
         , m_timestamp(timestamp)
     {
+        // Verify that timestamp is coming from monotonic clock and not the
+        // wall clock.
+        DCHECK(timestamp <= monotonicallyIncreasingTime());
     }
 
     // Explicit protected destructor so that people don't accidentally
     // delete a PlatformEvent.
     ~PlatformEvent()
     {
     }
 
     unsigned m_type;
     unsigned m_modifiers;
     double m_timestamp;
 };
 
 } // namespace blink
 
 #endif // PlatformEvent_h