Animation: Fix loss of type information when interpolating value of 0

Source/core/css/CSSPrimitiveValue.h

Index: Source/core/css/CSSPrimitiveValue.h
diff --git a/Source/core/css/CSSPrimitiveValue.h b/Source/core/css/CSSPrimitiveValue.h
index 277a2df595425ca2dd96a156a88bedbbc1fa2330..1190989028c438f2e304c47febadabd47733ff0c 100644
--- a/Source/core/css/CSSPrimitiveValue.h
+++ b/Source/core/css/CSSPrimitiveValue.h
@@ -26,6 +26,7 @@
 #include "core/CSSValueKeywords.h"
 #include "core/css/CSSValue.h"
 #include "platform/graphics/Color.h"
+#include "wtf/BitVector.h"
 #include "wtf/Forward.h"
 #include "wtf/MathExtras.h"
 #include "wtf/PassRefPtr.h"
@@ -150,7 +151,10 @@ public:
     };
 
     typedef Vector<double, CSSPrimitiveValue::LengthUnitTypeCount> CSSLengthArray;
+    typedef BitVector CSSLengthTypeArray;
+
     void accumulateLengthArray(CSSLengthArray&, double multiplier = 1) const;
+    void accumulateLengthArray(CSSLengthArray&, CSSLengthTypeArray&, double multiplier = 1) const;
 
     // This enum follows the BisonCSSParser::Units enum augmented with UNIT_FREQUENCY for frequencies.
     enum UnitCategory {
@@ -385,6 +389,7 @@ private:
 };
 
 typedef CSSPrimitiveValue::CSSLengthArray CSSLengthArray;
+typedef CSSPrimitiveValue::CSSLengthTypeArray CSSLengthTypeArray;
 
 DEFINE_CSS_VALUE_TYPE_CASTS(CSSPrimitiveValue, isPrimitiveValue());