Make sure to not return a negative containing block height when computing a

quirks percentage height containing block.  Bug 303005, r+sr=dbaron,
a=bsmedberg


git-svn-id: svn://10.0.0.236/trunk@177003 18797224-902f-48f8-a5cc-f745e15eee43

mozilla/layout/generic/nsHTMLReflowState.cpp

@@ -1561,7 +1561,8 @@ CalcQuirkContainingBlockHeight(const nsHTMLReflowState& aReflowState)
     break;
   }
 
-  return result;
+  // Make sure not to return a negative height here!
+  return PR_MAX(result, 0);
 }
 // Called by InitConstraints() to compute the containing block rectangle for
 // the element. Handles the special logic for absolutely positioned elements