Possible browser crash while traversing tree of accessibility objects.

ui/accessibility/platform/ax_platform_node_auralinux.cc

 // 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.
 
 #include "ui/accessibility/platform/ax_platform_node_auralinux.h"
 
 #include "base/command_line.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/task_runner.h"
 #include "ui/accessibility/ax_node_data.h"
@@ skipping 170 matching lines @@
 
   obj->GetAtkState(atk_state_set);
   return atk_state_set;
 }
 
 //
 // AtkComponent interface
 //
 
 static gfx::Point FindAtkObjectParentCoords(AtkObject* atk_object) {
+  if (!atk_object)
+    return gfx::Point(0, 0);
+
   if (atk_object_get_role(atk_object) == ATK_ROLE_WINDOW) {
     int x, y;
     atk_component_get_extents(ATK_COMPONENT(atk_object),
         &x, &y, nullptr, nullptr, ATK_XY_WINDOW);
     gfx::Point window_coords(x, y);
     return window_coords;
   }
   atk_object = atk_object_get_parent(atk_object);
 
   return FindAtkObjectParentCoords(atk_object);
@@ skipping 293 matching lines @@
   if (x)
     *x = extents.x();
   if (y)
     *y = extents.y();
   if (width)
     *width = extents.width();
   if (height)
     *height = extents.height();
 
   if (coord_type == ATK_XY_WINDOW) {
-    AtkObject* atk_object = GetParent();
-    gfx::Point window_coords = FindAtkObjectParentCoords(atk_object);
-    if (x)
-      *x -= window_coords.x();
-    if (y)
-      *y -= window_coords.y();
+    if (AtkObject* atk_object = GetParent()) {
+      gfx::Point window_coords = FindAtkObjectParentCoords(atk_object);
+      if (x)
+        *x -= window_coords.x();
+      if (y)
+        *y -= window_coords.y();
+    }
   }
 }
 
 void AXPlatformNodeAuraLinux::GetExtents(gint* x, gint* y,
                                          gint* width, gint* height,
                                          AtkCoordType coord_type) {
   SetExtentsRelativeToAtkCoordinateType(x, y,
                                         width, height,
                                         coord_type);
 }
 
 void AXPlatformNodeAuraLinux::GetPosition(gint* x, gint* y,
                                           AtkCoordType coord_type) {
   SetExtentsRelativeToAtkCoordinateType(x, y,
                                         nullptr,nullptr,
                                         coord_type);
 }
 
 void AXPlatformNodeAuraLinux::GetSize(gint* width, gint* height) {
   gfx::Rect rect_size = GetData().location;
   if (width)
     *width = rect_size.width();
   if (height)
     *height = rect_size.height();
 }
 
 }  // namespace ui