a11y: Move CreateTextMarker[Range] to TextMarkerHelperMac.

ui/accessibility/ax_abstract_position.cc

Index: ui/accessibility/ax_abstract_position.cc
diff --git a/ui/accessibility/ax_abstract_position.cc b/ui/accessibility/ax_abstract_position.cc
new file mode 100644
index 0000000000000000000000000000000000000000..61f5864234ee4b1563cd8661592fec514cda718c
--- /dev/null
+++ b/ui/accessibility/ax_abstract_position.cc
@@ -0,0 +1,20 @@
+// Copyright 2017 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 "ui/accessibility/ax_abstract_position.h"
+
+namespace ui {
+
+AXPositionPointer::AXPositionPointer(AXPositionPointer&& other) = default;
+AXPositionPointer::AXPositionPointer(nullptr_t) {}
+AXPositionPointer::~AXPositionPointer() = default;
+
+constexpr int AXAbstractPosition::INVALID_TREE_ID;
+constexpr int32_t AXAbstractPosition::INVALID_ANCHOR_ID;
+constexpr int AXAbstractPosition::BEFORE_TEXT;
+constexpr int AXAbstractPosition::INVALID_INDEX;
+constexpr int AXAbstractPosition::INVALID_OFFSET;
+constexpr AXPositionData AXAbstractPosition::kNullData;
+
+}  // namespace ui