Introduce enum class TextAffinity as replacement of enum EAffinity

Source/core/editing/InputMethodController.cpp

Index: Source/core/editing/InputMethodController.cpp
diff --git a/Source/core/editing/InputMethodController.cpp b/Source/core/editing/InputMethodController.cpp
index 5b5ef9b08a36f75d86bed79f86812e7ea6545f0b..2bf2ad38ce65beff5978579b85649c7055b6896b 100644
--- a/Source/core/editing/InputMethodController.cpp
+++ b/Source/core/editing/InputMethodController.cpp
@@ -299,7 +299,7 @@ void InputMethodController::setComposition(const String& text, const Vector<Comp
     unsigned start = std::min(baseOffset + selectionStart, extentOffset);
     unsigned end = std::min(std::max(start, baseOffset + selectionEnd), extentOffset);
     RefPtrWillBeRawPtr<Range> selectedRange = Range::create(baseNode->document(), baseNode, start, baseNode, end);
-    frame().selection().setSelectedRange(selectedRange.get(), DOWNSTREAM, FrameSelection::NonDirectional, NotUserTriggered);
+    frame().selection().setSelectedRange(selectedRange.get(), TextAffinity::Downstream, FrameSelection::NonDirectional, NotUserTriggered);
 }
 
 void InputMethodController::setCompositionFromExistingText(const Vector<CompositionUnderline>& underlines, unsigned compositionStart, unsigned compositionEnd)