Bug 1540737 - Don't use nsDisplayBorder's IsInvisibleInRect implementation for nsMathMLmtable, since it uses a custom style context. r=miko

Differential Revision: https://phabricator.services.mozilla.com/D114674

layout/mathml/nsMathMLmtableFrame.cpp

@@ -326,6 +326,10 @@ class nsDisplaymtdBorder final : public nsDisplayBorder {
       nsDisplayListBuilder* aDisplayListBuilder) override {
     return false;
   }
+
+  virtual bool IsInvisibleInRect(const nsRect& aRect) const override {
+    return false;
+  }
 };
 
 #ifdef DEBUG