Fix crash when calling get_accChild on empty WebView.

ui/views/accessibility/native_view_accessibility_win.cc

 // Copyright (c) 2012 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.
 
 #include "ui/views/accessibility/native_view_accessibility_win.h"
 
 #include <UIAutomationClient.h>
 #include <oleacc.h>
 
 #include <set>
@@ skipping 88 matching lines @@
       return accessible;
   }
 
   // Search all web views. For each one, first ensure it's a descendant
   // of this view where the event was posted - and if so, see if it owns
   // an accessible object with that child id. If so, save the view to speed
   // up the next notification.
   for (std::set<View*>::iterator iter = web_views_.begin();
        iter != web_views_.end(); ++iter) {
     View* web_view = *iter;
-    if (!top_view->Contains(web_view))
+    if (top_view == web_view || !top_view->Contains(web_view))
       continue;
     IAccessible* accessible = AccessibleObjectFromChildId(web_view, child_id);
     if (accessible) {
       last_top_view_ = top_view;
       last_web_view_ = web_view;
       return accessible;
     }
   }
 
   return NULL;
@@ skipping 1169 matching lines @@
     LONG start_offset,
     ui::TextBoundaryDirection direction) {
   HandleSpecialTextOffset(text, &start_offset);
   ui::TextBoundaryType boundary = IA2TextBoundaryToTextBoundary(ia2_boundary);
   std::vector<int32> line_breaks;
   return ui::FindAccessibleTextBoundary(
       text, line_breaks, boundary, start_offset, direction);
 }
 
 }  // namespace views