Expose internal treegrid role, do some cleanup for table/grid/treegrid handling

third_party/WebKit/Source/modules/accessibility/AXARIAGrid.h

Index: third_party/WebKit/Source/modules/accessibility/AXARIAGrid.h
diff --git a/third_party/WebKit/Source/modules/accessibility/AXARIAGrid.h b/third_party/WebKit/Source/modules/accessibility/AXARIAGrid.h
index ccd3b7f93b694abed6edd507617e1fe2c73517d4..f21c07cc162ac5569f9529407d7a082d64d2de16 100644
--- a/third_party/WebKit/Source/modules/accessibility/AXARIAGrid.h
+++ b/third_party/WebKit/Source/modules/accessibility/AXARIAGrid.h
@@ -48,6 +48,10 @@ class AXARIAGrid final : public AXTable {
 
   bool IsAriaTable() const override { return true; }
 
+  AccessibilityRole RoleValue() const final {
+    return AXLayoutObject::RoleValue();
+  }  // Use ARIA role
+
   void AddChildren() override;
 
  private: