Decouple font unit conversion in computeLengthDouble from RenderStyle.

Source/core/css/CSSPrimitiveValue.cpp

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2012 Apple Inc. All rights reserved.
  *
  * 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
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 586 matching lines @@
 }
 
 double CSSPrimitiveValue::computeLengthDouble(const CSSToLengthConversionData& conversionData)
 {
     // The logic in this function is duplicated in MediaValues::computeLength
     // because MediaValues::computeLength needs nearly identical logic, but we haven't found a way to make
     // CSSPrimitiveValue::computeLengthDouble more generic (to solve both cases) without hurting performance.
     if (m_primitiveUnitType == CSS_CALC)
         return m_value.calc->computeLengthPx(conversionData);
 
-    const RenderStyle& style = conversionData.style();
-    const RenderStyle* rootStyle = conversionData.rootStyle();
-    bool computingFontSize = conversionData.computingFontSize();
-
     double factor;
 
     switch (primitiveType()) {
         case CSS_EMS:
-            factor = computingFontSize ? style.fontDescription().specifiedSize() : style.fontDescription().computedSize();
+            factor = conversionData.emFontSize();
             break;
         case CSS_EXS:
-            // FIXME: We have a bug right now where the zoom will be applied twice to EX units.
-            // We really need to compute EX using fontMetrics for the original specifiedSize and not use
-            // our actual constructed rendering font.
-            if (style.fontMetrics().hasXHeight())
-                factor = style.fontMetrics().xHeight();
-            else
-                factor = (computingFontSize ? style.fontDescription().specifiedSize() : style.fontDescription().computedSize()) / 2.0;
+            factor = conversionData.exFontSize();
             break;
         case CSS_REMS:
-            if (rootStyle)
-                factor = computingFontSize ? rootStyle->fontDescription().specifiedSize() : rootStyle->fontDescription().computedSize();
-            else
-                factor = 1.0;
+            factor = conversionData.remFontSize();
             break;
         case CSS_CHS:
-            factor = style.fontMetrics().zeroWidth();
+            factor = conversionData.chFontSize();
             break;
         case CSS_PX:
             factor = 1.0;
             break;
         case CSS_CM:
             factor = cssPixelsPerCentimeter;
             break;
         case CSS_MM:
             factor = cssPixelsPerMillimeter;
             break;
@@ skipping 24 matching lines @@
             return -1.0;
         default:
             ASSERT_NOT_REACHED();
             return -1.0;
     }
 
     // We do not apply the zoom factor when we are computing the value of the font-size property. The zooming
     // for font sizes is much more complicated, since we have to worry about enforcing the minimum font size preference
     // as well as enforcing the implicit "smart minimum."
     double result = getDoubleValue() * factor;
-    if (computingFontSize || isFontRelativeLength())
+    if (isFontRelativeLength())
         return result;
 
     return result * conversionData.zoom();
 }
 
 void CSSPrimitiveValue::accumulateLengthArray(CSSLengthArray& lengthArray, double multiplier) const
 {
     ASSERT(lengthArray.size() == LengthUnitTypeCount);
 
     if (m_primitiveUnitType == CSS_CALC) {
@@ skipping 736 matching lines @@
         visitor->trace(m_value.shape);
         break;
     default:
         break;
     }
 #endif
     CSSValue::traceAfterDispatch(visitor);
 }
 
 } // namespace blink