MacViews/a11y: Allow accessibility clients to update the selected text.

ui/accessibility/platform/ax_platform_node_delegate.h

 // 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.
 
 #ifndef UI_ACCESSIBILITY_PLATFORM_AX_PLATFORM_NODE_DELEGATE_H_
 #define UI_ACCESSIBILITY_PLATFORM_AX_PLATFORM_NODE_DELEGATE_H_
 
 #include "ui/accessibility/ax_enums.h"
 #include "ui/accessibility/ax_export.h"
 #include "ui/gfx/geometry/vector2d.h"
@@ skipping 67 matching lines @@
 
   //
   // Actions.
   //
 
   // Perform the default action, e.g. click a button, follow a link, or
   // toggle a checkbox.
   virtual void DoDefaultAction() = 0;
 
   // Change the value of a control, such as the text content of a text field.
-  virtual bool SetStringValue(const base::string16& new_value) = 0;
+  // If |clear_first| is true, this replaces all text with the |new_value|.
+  // Otherwise this inserts |new_value| at the cursor position, replacing any
+  // selected text. The cursor is placed at the end of |new_value|.
+  virtual bool SetStringValue(const base::string16& new_value,
+                              bool clear_first) = 0;
 
-  // Whether the string value is settable.
+  // Whether SetStringValue() is callable, i.e. if the string value is not read
+  // only and if the callback exists.
   virtual bool CanSetStringValue() = 0;
 };
 
 }  // namespace ui
 
 #endif  // UI_ACCESSIBILITY_PLATFORM_AX_PLATFORM_NODE_DELEGATE_H_