Keep effectiveZoom finite

Source/core/style/ComputedStyle.h

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 1869 matching lines @@
 {
     if (compareEqual(visual->m_zoom, f))
         return false;
     visual.access()->m_zoom = f;
     setEffectiveZoom(effectiveZoom() * zoom());
     return true;
 }
 
 inline bool ComputedStyle::setEffectiveZoom(float f)
 {
-    if (compareEqual(rareInheritedData->m_effectiveZoom, f))
+    float clampedEffectiveZoom = clampTo<float>(f);

[fs, 2015/06/23 21:11:57]

In practice this is just a "gratuitous max value" - a fairly large one at that.
Could (should?) quite possibly be a smaller value. With this value, it still
fairly trivial to overflow to Infinity (multiplication with anything > 1 will do
it for instance). It works better than the actual Infinity though, because a
quite common operation/case is "0 * Infinity => NaN" (value == 0, zoom ==
Infinity), which now becomes "0 * max() => 0". Will change to smaller value for
no fee at all.

+    if (compareEqual(rareInheritedData->m_effectiveZoom, clampedEffectiveZoom))
         return false;
-    rareInheritedData.access()->m_effectiveZoom = f;
+    rareInheritedData.access()->m_effectiveZoom = clampedEffectiveZoom;
     return true;
 }
 
 inline bool ComputedStyle::isSharable() const
 {
     if (unique())
         return false;
     if (hasUniquePseudoStyle())
         return false;
     return true;
@@ skipping 28 matching lines @@
 }
 
 inline bool ComputedStyle::hasPseudoElementStyle() const
 {
     return noninherited_flags.pseudoBits & PSEUDO_ELEMENT_MASK;
 }
 
 } // namespace blink
 
 #endif // ComputedStyle_h