Make web content accessibility tree a descendant of main window's tree again

ui/gfx/native_widget_types.h

Index: ui/gfx/native_widget_types.h
===================================================================
--- ui/gfx/native_widget_types.h	(revision 88807)
+++ ui/gfx/native_widget_types.h	(working copy)
@@ -39,6 +39,7 @@
 #if defined(OS_WIN)
 #include <windows.h>  // NOLINT
 typedef struct HFONT__* HFONT;
+struct IAccessible;
 #elif defined(OS_MACOSX)
 struct CGContext;
 #ifdef __OBJC__
@@ -76,6 +77,7 @@
 typedef HCURSOR NativeCursor;
 typedef HMENU NativeMenu;
 typedef HRGN NativeRegion;
+typedef IAccessible* NativeViewAccessible;
 #elif defined(OS_MACOSX)
 typedef NSFont* NativeFont;
 typedef NSView* NativeView;
@@ -84,6 +86,7 @@
 typedef CGContext* NativeDrawingContext;
 typedef void* NativeCursor;
 typedef void* NativeMenu;
+typedef void* NativeViewAccessible;
 #elif defined(USE_X11)
 typedef PangoFontDescription* NativeFont;
 typedef GtkWidget* NativeView;
@@ -93,6 +96,7 @@
 typedef GdkCursor* NativeCursor;
 typedef GtkWidget* NativeMenu;
 typedef GdkRegion* NativeRegion;
+typedef void* NativeViewAccessible;
 #endif
 
 #if defined(OS_MACOSX)