Support negative weight for edges.

script/features/algorithms/model/plugins/MaxFlow.js

@@ -188,13 +188,13 @@ FindMaxFlow.prototype.getPriority = function()
 }
 
 // @return true, if you change resotry graph after use.
-BaseAlgorithm.prototype.wantRestore = function()
+FindMaxFlow.prototype.wantRestore = function()
 {
     return true;
 }
 
 // calls this method if wantRestore return true.
-BaseAlgorithm.prototype.restore = function()
+FindMaxFlow.prototype.restore = function()
 {
     if (this.selectedEdges != null)
     {
@@ -216,6 +216,11 @@ BaseAlgorithm.prototype.restore = function()
     }
 }
 
+FindMaxFlow.prototype.IsSupportNegativeWeight = function()
+{
+    return true;
+}
+
 
 // Factory for connected components.
 function CreateFindMaxFlow(graph, app)