Compute snap offsets (both repeat and element based)

Source/platform/LengthFunctions.cpp

Index: Source/platform/LengthFunctions.cpp
diff --git a/Source/platform/LengthFunctions.cpp b/Source/platform/LengthFunctions.cpp
index 5894d0bb406376173c56cdd6f0282e87501b1ea4..22d6c2f92bed55e901b87490ad7cbbf119eccc98 100644
--- a/Source/platform/LengthFunctions.cpp
+++ b/Source/platform/LengthFunctions.cpp
@@ -25,6 +25,7 @@
 #include "platform/LengthFunctions.h"
 
 #include "platform/LayoutUnit.h"
+#include "platform/LengthPoint.h"
 #include "platform/LengthSize.h"
 
 namespace blink {
@@ -129,4 +130,9 @@ FloatSize floatSizeForLengthSize(const LengthSize& lengthSize, const FloatSize&
     return FloatSize(floatValueForLength(lengthSize.width(), boxSize.width()), floatValueForLength(lengthSize.height(), boxSize.height()));
 }
 
+FloatPoint floatPointForLengthPoint(const LengthPoint& LengthPoint, const FloatSize& boxSize)
+{
+    return FloatPoint(floatValueForLength(LengthPoint.x(), boxSize.width()), floatValueForLength(LengthPoint.y(), boxSize.height()));
+}
+
 } // namespace blink