Fix problems with flakes in SVG LayoutTests by reordering arithmetic.

Source/core/svg/SVGLength.cpp

Index: Source/core/svg/SVGLength.cpp
diff --git a/Source/core/svg/SVGLength.cpp b/Source/core/svg/SVGLength.cpp
index 3c928704dc21593d6dd2cd672f1f622760e1dea7..10db3a15c50f7b27e3198469354636cfb07e5e0e 100644
--- a/Source/core/svg/SVGLength.cpp
+++ b/Source/core/svg/SVGLength.cpp
@@ -186,12 +186,33 @@ void SVGLength::setUnitType(SVGLengthType type)
 float SVGLength::valueAsPercentage() const
 {
     // 100% = 100.0 instead of 1.0 for historical reasons, this could eventually be changed

[Stephen Chennney, 2015/01/22 21:57:25]

This comment seems wrong now.

[Daniel Bratell, 2015/01/23 08:49:40]

It is still correct since it refers to the internal representation of
LengthTypePercentage. I will rephrase them though, so that it's more clear.

-    if (m_unitType == LengthTypePercentage)
+    if (m_unitType == LengthTypePercentage) {
+        // Note: This division is a source of floating point inaccuracy.
         return m_valueInSpecifiedUnits / 100;
+    }
 
     return m_valueInSpecifiedUnits;
 }
 
+float SVGLength::valueAsPercentage100() const
+{
+    // 100% = 100.0 instead of 1.0 for historical reasons, this could eventually be changed
+    if (m_unitType == LengthTypePercentage)
+        return m_valueInSpecifiedUnits;
+
+    return m_valueInSpecifiedUnits * 100;
+}
+
+float SVGLength::scaleByPercentage(float input) const
+{
+    float result = input * m_valueInSpecifiedUnits;
+    if (m_unitType == LengthTypePercentage) {
+        // Delaying division by 100 as long as possible since it introduces floating point errors.
+        result = result / 100;
+    }
+    return result;
+}
+
 template<typename CharType>
 static bool parseValueInternal(const String& string, float& convertedNumber, SVGLengthType& type)
 {
@@ -403,8 +424,8 @@ PassRefPtrWillBeRawPtr<SVGLength> SVGLength::blend(PassRefPtrWillBeRawPtr<SVGLen
     RefPtrWillBeRawPtr<SVGLength> length = create();
 
     if (fromType == LengthTypePercentage || toType == LengthTypePercentage) {
-        float fromPercent = from->valueAsPercentage() * 100;
-        float toPercent = valueAsPercentage() * 100;
+        float fromPercent = from->valueAsPercentage100();
+        float toPercent = valueAsPercentage100();
         length->newValueSpecifiedUnits(LengthTypePercentage, blink::blend(fromPercent, toPercent, progress));
         return length;
     }