Do not treat '0' as 'none' for font-size-adjust

Source/core/css/resolver/FontBuilder.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Google Inc. All rights reserved.
  * Copyright (C) 2015 Collabora Ltd. 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.
@@ skipping 311 matching lines @@
     if (!specifiedSize && fontDescription.keywordSize())
         specifiedSize = FontSize::fontSizeForKeyword(&m_document, fontDescription.keywordSize(), fontDescription.fixedPitchFontType());
 
     fontDescription.setSpecifiedSize(specifiedSize);
 
     checkForGenericFamilyChange(style.fontDescription(), fontDescription);
 }
 
 void FontBuilder::updateAdjustedSize(FontDescription& fontDescription, const LayoutStyle& style, FontSelector* fontSelector)
 {
-    const float sizeAdjust = fontDescription.sizeAdjust();
     const float specifiedSize = fontDescription.specifiedSize();
-    if (!sizeAdjust || !specifiedSize)
+    if (!fontDescription.hasSizeAdjust() || !specifiedSize)
         return;
 
     // We need to create a temporal Font to get xHeight of a primary font.
     // The aspect value is based on the xHeight of the font for the computed font size,
-    // so we need to reset the adjustment.
-    fontDescription.setAdjustedSize(0);
+    // so we need to reset the adjustedSize to computedSize. See FontDescription::effectiveFontSize.
+    fontDescription.setAdjustedSize(fontDescription.computedSize());
 
     Font font(fontDescription);
     font.update(fontSelector);
     if (!font.fontMetrics().hasXHeight())
         return;
 
+    const float sizeAdjust = fontDescription.sizeAdjust();
     float aspectValue = font.fontMetrics().xHeight() / specifiedSize;
     float adjustedSize = (sizeAdjust / aspectValue) * specifiedSize;
     adjustedSize = getComputedSizeFromSpecifiedSize(fontDescription, style.effectiveZoom(), adjustedSize);
 
     float multiplier = style.textAutosizingMultiplier();
     if (multiplier > 1)
         adjustedSize = TextAutosizer::computeAutosizedFontSize(adjustedSize, multiplier);
     fontDescription.setAdjustedSize(adjustedSize);
 }
 
@@ skipping 72 matching lines @@
     FontOrientation fontOrientation;
     NonCJKGlyphOrientation glyphOrientation;
     getFontAndGlyphOrientation(documentStyle, fontOrientation, glyphOrientation);
     fontDescription.setOrientation(fontOrientation);
     fontDescription.setNonCJKGlyphOrientation(glyphOrientation);
     documentStyle.setFontDescription(fontDescription);
     documentStyle.font().update(fontSelector);
 }
 
 }