Fix bug 347495 - Invalid-markup message doesn't disappear when MathML gets valid again, r+sr=roc

layout/mathml/base/src/nsMathMLContainerFrame.h

@@ -147,6 +147,13 @@ public:
          const nsHTMLReflowState& aReflowState,
          nsReflowStatus&          aStatus);
 
+  NS_IMETHOD
+  WillReflow(nsPresContext* aPresContext)
+  {
+    mPresentationData.flags &= ~NS_MATHML_ERROR;
+    return nsHTMLContainerFrame::WillReflow(aPresContext);
+  }
+
   NS_IMETHOD
   DidReflow(nsPresContext*           aPresContext,
             const nsHTMLReflowState*  aReflowState,