Merge 127933

Source/WebCore/platform/FractionalLayoutUnit.h

 /*
  * Copyright (c) 2012, 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 164 matching lines @@
         FractionalLayoutUnit m;
         m.m_value = std::numeric_limits<int>::max();
         return m;
     }
     static const FractionalLayoutUnit min()
     {
         FractionalLayoutUnit m;
         m.m_value = std::numeric_limits<int>::min();
         return m;
     }
+
+    // Versions of max/min that are slightly smaller/larger than max/min() to allow for roinding without overflowing.
+    static const FractionalLayoutUnit nearlyMax()
+    {
+        FractionalLayoutUnit m;
+        m.m_value = std::numeric_limits<int>::max() - kFixedPointDenominator / 2;
+        return m;
+    }
+    static const FractionalLayoutUnit nearlyMin()
+    {
+        FractionalLayoutUnit m;
+        m.m_value = std::numeric_limits<int>::min() + kFixedPointDenominator / 2;
+        return m;
+    }
+    
     static FractionalLayoutUnit clamp(double value)
     {
         return clampTo<FractionalLayoutUnit>(value, FractionalLayoutUnit::min(), FractionalLayoutUnit::max());
     }
     
 private:
     static bool isInBounds(int value)
     {
         return ::abs(value) <= std::numeric_limits<int>::max() / kFixedPointDenominator;
     }
@@ skipping 483 matching lines @@
 }
 
 inline float& operator/=(float& a, const FractionalLayoutUnit& b)
 {
     a = a / b;
     return a;
 }
 
 inline int snapSizeToPixel(FractionalLayoutUnit size, FractionalLayoutUnit location) 
 {
-    return (location + size).round() - location.round();
+    FractionalLayoutUnit fraction = location - location.floor();
+    return (fraction + size).round() - fraction.round();
 }
 
 #if PLATFORM(QT)
 inline QDataStream& operator<<(QDataStream& stream, const FractionalLayoutUnit& value)
 {
     if (kFixedPointDenominator == 1)
         stream << value.rawValue();
     else
         stream << QString::fromLatin1("%1").arg(value.toFloat(), 0, 'f', 2);
 
     return stream;
 }
 
 inline QDataStream& operator>>(QDataStream& stream, FractionalLayoutUnit& value)
 {
     float v;
     stream >> v;
     value = v;
     return stream;
 }
 #endif
 
 } // namespace WebCore
 
 #endif // FractionalLayoutUnit_h