Limit ScrollAnchor to 20 adjustments between user scrolls.

third_party/WebKit/Source/core/layout/ScrollAnchor.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ScrollAnchor_h
 #define ScrollAnchor_h
 
 #include "core/CoreExport.h"
 #include "platform/geometry/LayoutPoint.h"
 #include "platform/heap/Handle.h"
@@ skipping 103 matching lines @@
 
     // The anchor point that was used for the most recent non-zero adjustment.
     AnchorPoint m_lastAdjusted;
 
     // The size of the most recent non-zero adjustment.
     IntSize m_lastAdjustment;
 
     // True iff the last adjustment was the exact opposite of the one before it.
     // A bounce suggests a circular interaction with a scroll event handler.
     bool m_hasBounced;
+
+    // Number of adjustments made since the last clear().
+    int m_adjustmentCount;
 };
 
 } // namespace blink
 
 #endif // ScrollAnchor_h