Introduce enum class TextAffinity as replacement of enum EAffinity

Source/core/editing/VisibleUnitsTest.cpp

Index: Source/core/editing/VisibleUnitsTest.cpp
diff --git a/Source/core/editing/VisibleUnitsTest.cpp b/Source/core/editing/VisibleUnitsTest.cpp
index cb084c695f7edee13c32e6da2069e28a46a1f379..db26ff655d43b07e89b3315bb6cbdf13cd638de2 100644
--- a/Source/core/editing/VisibleUnitsTest.cpp
+++ b/Source/core/editing/VisibleUnitsTest.cpp
@@ -12,12 +12,12 @@ namespace blink {
 
 namespace {
 
-PositionWithAffinity positionWithAffinityInDOMTree(Node& anchor, int offset, EAffinity affinity = DOWNSTREAM)
+PositionWithAffinity positionWithAffinityInDOMTree(Node& anchor, int offset, TextAffinity affinity = TextAffinity::Downstream)
 {
     return PositionWithAffinity(canonicalPositionOf(Position(&anchor, offset)), affinity);
 }
 
-PositionInComposedTreeWithAffinity positionWithAffinityInComposedTree(Node& anchor, int offset, EAffinity affinity = DOWNSTREAM)
+PositionInComposedTreeWithAffinity positionWithAffinityInComposedTree(Node& anchor, int offset, TextAffinity affinity = TextAffinity::Downstream)
 {
     return PositionInComposedTreeWithAffinity(canonicalPositionOf(PositionInComposedTree(&anchor, offset)), affinity);
 }