Move PositionWithAffinity class to editing

Source/core/editing/PositionWithAffinity.cpp

Index: Source/core/editing/PositionWithAffinity.cpp
diff --git a/Source/core/editing/PositionWithAffinity.cpp b/Source/core/editing/PositionWithAffinity.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..0477886b13b036bfc24bb0d33f3d7f3496c044b3
--- /dev/null
+++ b/Source/core/editing/PositionWithAffinity.cpp
@@ -0,0 +1,30 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file./*
+
+#include "config.h"
+#include "core/editing/PositionWithAffinity.h"
+
+namespace WebCore {
+
+PositionWithAffinity::PositionWithAffinity(const Position& position, EAffinity affinity)
+    : m_position(position)
+    , m_affinity(affinity)
+{
+}
+
+PositionWithAffinity::PositionWithAffinity()
+    : m_affinity(DOWNSTREAM)
+{
+}
+
+PositionWithAffinity::~PositionWithAffinity()
+{
+}
+
+void PositionWithAffinity::trace(Visitor* visitor)
+{
+    visitor->trace(m_position);
+}
+
+} // namespace WebCore