a11y: Move CreateTextMarker[Range] to TextMarkerHelperMac.

ui/accessibility/platform/text_marker_helper_mac.h

+// 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.
+
+#ifndef UI_ACCESSIBILITY_PLATFORM_TEXT_MARKER_HELPER_MAC_H_
+#define UI_ACCESSIBILITY_PLATFORM_TEXT_MARKER_HELPER_MAC_H_
+
+#import <Foundation/Foundation.h>
+
+#include "ui/accessibility/ax_abstract_position.h"
+#include "ui/accessibility/ax_export.h"
+
+namespace ui {
+
+// Provides concrete a AXPosition from the source AXNode for initial text marker
+// requests.
+class AX_EXPORT PositionFactory {
+ public:
+  PositionFactory() {}
+  virtual ~PositionFactory() {}
+
+  virtual AXPositionPointer GetRoot() const = 0;
+  virtual AXRangePointer GetSelection() const = 0;
+  virtual AXPositionPointer GetFromData(const AXPositionData& data) const = 0;
+  virtual id GetAccessibilityObject(const AXPositionData& data) const = 0;
+};
+
+}  // namespace ui
+
+// A component that can be placed in an AXNode to satisfy requests from Cocoa
+// accessibility to create and manipulate AXTextMarker objects.
+AX_EXPORT
+@interface TextMarkerHelperMac : NSObject
+
+- (instancetype)initWithFactory:(std::unique_ptr<ui::PositionFactory>)factory;
+
+// Returns a text marker that points to the first character in the document that
+// can be selected with VoiceOver.
+- (id)startTextMarker;
+
+// Returns a text marker that points to the last character in the document that
+// can be selected with VoiceOver.
+- (id)endTextMarker;
+
+// Returns a text marker range corresponding to the current selection.
+- (id)selectedTextMarkerRange;
+
+// Given an AXTextMarkerRangeRef, extract the stored AXPositionData for the
+// start and end markers. Returns NO if either marker is nil, or if the stored
+// data is the wrong size.
++ (BOOL)getRangeDataFromMarkerRange:(id)parameter
+                              start:(ui::AXPositionData*)start
+                                end:(ui::AXPositionData*)end;
+
+@end
+
+#endif  // UI_ACCESSIBILITY_PLATFORM_TEXT_MARKER_HELPER_MAC_H_