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

ui/views/controls/textfield/textfield.h

Index: ui/views/controls/textfield/textfield.h
diff --git a/ui/views/controls/textfield/textfield.h b/ui/views/controls/textfield/textfield.h
index 55353ee8a4874498dbeff19c73dd9df4b11a7c6d..1723fb923f850ec9451a5bf60b85654cbd691d41 100644
--- a/ui/views/controls/textfield/textfield.h
+++ b/ui/views/controls/textfield/textfield.h
@@ -347,8 +347,10 @@ class VIEWS_EXPORT Textfield : public View,
 
   // Handles a request to change the value of this text field from software
   // using an accessibility API (typically automation software, screen readers
-  // don't normally use this). Sets the value and clears the selection.
-  void AccessibilitySetValue(const base::string16& new_value);
+  // don't normally use this). If |clear_first| is true, clears the existing
+  // value first and sets it to |new_value|. If false, deletes whatever's
+  // selected and replaces it with |new_value|. Then clears the text selection.
+  void AccessibilitySetValue(const base::string16& new_value, bool clear_first);
 
   // Updates the painted background color.
   void UpdateBackgroundColor();