Better handle null delegates by returning instead of CHECK()

ui/accessibility/platform/ax_platform_node_win.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 <atlbase.h>
 #include <atlcom.h>
 #include <limits.h>
 #include <oleacc.h>
 #include <stdint.h>
 
@@ skipping 1363 matching lines @@
 
 STDMETHODIMP AXPlatformNodeWin::get_columnHeaderCells(
     IUnknown*** cell_accessibles,
     long* n_column_header_cells) {
   if (!cell_accessibles || !n_column_header_cells)
     return E_INVALIDARG;
 
   *n_column_header_cells = 0;
   auto* table = GetTable();
   if (!table) {
-    NOTREACHED();
     return S_FALSE;
   }
 
   int column = GetTableColumn();
   int columns = GetTableColumnCount();
   int rows = GetTableRowCount();
   if (columns <= 0 || rows <= 0 || column < 0 || column >= columns)
     return S_FALSE;
 
   for (int i = 0; i < rows; ++i) {
@@ skipping 36 matching lines @@
 }
 
 STDMETHODIMP AXPlatformNodeWin::get_rowHeaderCells(IUnknown*** cell_accessibles,
                                                    long* n_row_header_cells) {
   if (!cell_accessibles || !n_row_header_cells)
     return E_INVALIDARG;
 
   *n_row_header_cells = 0;
   auto* table = GetTable();
   if (!table) {
-    NOTREACHED();
     return S_FALSE;
   }
 
   int row = GetTableRow();
   int columns = GetTableColumnCount();
   int rows = GetTableRowCount();
   if (columns <= 0 || rows <= 0 || row < 0 || row >= rows)
     return S_FALSE;
 
   for (int i = 0; i < columns; ++i) {
@@ skipping 1310 matching lines @@
   if (container && container->GetData().role == ui::AX_ROLE_GROUP)
     container = FromNativeViewAccessible(container->GetParent());
 
   if (!container)
     return false;
 
   return container->GetData().role == ui::AX_ROLE_TREE_GRID;
 }
 
 }  // namespace ui