diff -r 000000000000 -r 6474c204b198 accessible/src/generic/ARIAGridAccessible-inl.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/accessible/src/generic/ARIAGridAccessible-inl.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,59 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_a11y_ARIAGridAccessible_inl_h__
+#define mozilla_a11y_ARIAGridAccessible_inl_h__
+
+#include "ARIAGridAccessible.h"
+
+#include "AccIterator.h"
+
+namespace mozilla {
+namespace a11y {
+
+inline Accessible*
+ARIAGridCellAccessible::TableFor(Accessible* aRow) const
+{
+  if (aRow) {
+    Accessible* table = aRow->Parent();
+    if (table) {
+      roles::Role tableRole = table->Role();
+      if (tableRole == roles::GROUPING) { // if there's a rowgroup.
+        table = table->Parent();
+        if (table)
+          tableRole = table->Role();
+      }
+
+      return tableRole == roles::TABLE || tableRole == roles::TREE_TABLE ?
+        table : nullptr;
+    }
+  }
+
+  return nullptr;
+}
+
+inline int32_t
+ARIAGridCellAccessible::RowIndexFor(Accessible* aRow) const
+{
+  Accessible* table = TableFor(aRow);
+  if (table) {
+    int32_t rowIdx = 0;
+    Accessible* row = nullptr;
+    AccIterator rowIter(table, filters::GetRow);
+    while ((row = rowIter.Next()) && row != aRow)
+      rowIdx++;
+
+    if (row)
+      return rowIdx;
+  }
+
+  return -1;
+}
+
+} // namespace a11y
+} // namespace mozilla
+
+#endif