Add assertion to catch issues like bug 312704. r=mrbkap, sr=sicking

git-svn-id: svn://10.0.0.236/trunk@199490 18797224-902f-48f8-a5cc-f745e15eee43

mozilla/content/html/document/src/nsHTMLContentSink.cpp

@@ -1198,6 +1198,9 @@ SinkContext::CloseContainer(const nsHTMLTag aTag, PRBool aMalformed)
   --mStackPos;
   nsHTMLTag nodeType = mStack[mStackPos].mType;
 
+  NS_ASSERTION(nodeType == aTag,
+               "Tag mismatch.  Closing tag on wrong context or something?");
+
   nsGenericHTMLElement* content = mStack[mStackPos].mContent;
 
   content->Compact();