Clamp 'zoom' in CSSToLengthConversionData.

Source/core/css/CSSToLengthConversionData.cpp

 /*
  * Copyright (C) 2013 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 59 matching lines @@
 CSSToLengthConversionData::ViewportSize::ViewportSize(const RenderView* renderView)
     : m_width(renderView ? renderView->layoutViewportWidth() : 0)
     , m_height(renderView ? renderView->layoutViewportHeight() : 0)
 {
 }
 
 CSSToLengthConversionData::CSSToLengthConversionData(const RenderStyle* style, const FontSizes& fontSizes, const ViewportSize& viewportSize, float zoom)
     : m_style(style)
     , m_fontSizes(fontSizes)
     , m_viewportSize(viewportSize)
-    , m_zoom(zoom)
+    , m_zoom(clampTo<float>(zoom, std::numeric_limits<float>::denorm_min()))
 {
     ASSERT(m_style);
-    ASSERT(zoom > 0);
 }
 
 CSSToLengthConversionData::CSSToLengthConversionData(const RenderStyle* style, const RenderStyle* rootStyle, const RenderView* renderView, float zoom)
     : CSSToLengthConversionData(style, FontSizes(style, rootStyle), ViewportSize(renderView), zoom)
 {
 }
 
 double CSSToLengthConversionData::viewportWidthPercent() const
 {
     m_style->setHasViewportUnits();
     return m_viewportSize.width() / 100;
 }
 double CSSToLengthConversionData::viewportHeightPercent() const
 {
     m_style->setHasViewportUnits();
     return m_viewportSize.height() / 100;
 }
 double CSSToLengthConversionData::viewportMinPercent() const
 {
     m_style->setHasViewportUnits();
     return std::min(m_viewportSize.width(), m_viewportSize.height()) / 100;
 }
 double CSSToLengthConversionData::viewportMaxPercent() const
 {
     m_style->setHasViewportUnits();
     return std::max(m_viewportSize.width(), m_viewportSize.height()) / 100;
 }
 
 } // namespace blink