Disable navigations in the unload handler.

third_party/WebKit/Source/core/frame/UseCounter.h

 /*
  * Copyright (C) 2012 Google, 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
@@ skipping 1158 matching lines @@
         UntrustedEventDefaultHandled = 1372,
         // The following two items (FixedRasterScale*) are unused.
         FixedRasterScaleBlurryContent = 1373,
         FixedRasterScalePotentialPerformanceRegression = 1374,
         CSSDeepCombinatorAndShadow = 1375,
         OpacityWithPreserve3DQuirk = 1376,
         CSSSelectorPseudoReadOnly = 1377,
         CSSSelectorPseudoReadWrite = 1378,
         // The above items are available in M52 branch
 
-        UnloadHandler_Navigation = 1379,
         TouchStartUserGestureUtilized = 1380,
         TouchMoveUserGestureUtilized = 1381,
         TouchEndDuringScrollUserGestureUtilized = 1382,
         CSSSelectorPseudoDefined = 1383,
         RTCPeerConnectionAddIceCandidatePromise = 1384,
         RTCPeerConnectionAddIceCandidateLegacy = 1385,
         RTCIceCandidateDefaultSdpMLineIndex = 1386,
         DocumentCreateEventSensorErrorEvent = 1387,
         DocumentCreateEventSensorReadingEvent = 1388,
         MediaStreamConstraintsOldAndNew = 1389,
@@ skipping 183 matching lines @@
     friend class UseCounterTest;
     unsigned m_muteCount;
 
     CountBits m_countBits;
     BitVector m_CSSFeatureBits;
 };
 
 } // namespace blink
 
 #endif // UseCounter_h