Forward AXPlatformNodeWin calls to the right child.

ui/accessibility/platform/ax_platform_node_win.h

 // Copyright 2015 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_WIN_H_
 #define UI_ACCESSIBILITY_PLATFORM_AX_PLATFORM_NODE_WIN_H_
 
 #include <atlbase.h>
 #include <atlcom.h>
 #include <oleacc.h>
@@ skipping 255 matching lines @@
                             REFIID riid,
                             void** object) override;
 
  protected:
   AXPlatformNodeWin();
 
   // AXPlatformNodeBase overrides.
   void Dispose() override;
 
  private:
-  bool IsValidId(const VARIANT& child) const;
   int MSAARole();
   int MSAAState();
   int MSAAEvent(ui::AXEvent event);
 
   HRESULT GetStringAttributeAsBstr(
       ui::AXStringAttribute attribute,
       BSTR* value_bstr) const;
 
   void AddAlertTarget();
   void RemoveAlertTarget();
 
   // Return the text to use for IAccessibleText.
   base::string16 TextForIAccessibleText();
 
   // If offset is a member of IA2TextSpecialOffsets this function updates the
   // value of offset and returns, otherwise offset remains unchanged.
   void HandleSpecialTextOffset(LONG* offset);
 
   // Convert from a IA2TextBoundaryType to a ui::TextBoundaryType.
   ui::TextBoundaryType IA2TextBoundaryToTextBoundary(IA2TextBoundaryType type);
 
   // Search forwards (direction == 1) or backwards (direction == -1)
   // from the given offset until the given boundary is found, and
   // return the offset of that boundary.
   LONG FindBoundary(const base::string16& text,
                     IA2TextBoundaryType ia2_boundary,
                     LONG start_offset,
                     ui::TextBoundaryDirection direction);
+
+  // Many MSAA methods take a var_id parameter indicating that the operation
+  // should be performed on a particular child ID, rather than this object.
+  // This method tries to figure out the target object from |var_id| and
+  // returns a pointer to the target object if it exists, otherwise nullptr.
+  // Does not return a new reference.
+  AXPlatformNodeWin* GetTargetFromChildID(const VARIANT& var_id);
 };
 
 }  // namespace ui
 
 #endif  // UI_ACCESSIBILITY_PLATFORM_AX_PLATFORM_NODE_WIN_H_