Support for negative numbers in computed bindings

test/unit/bind-elements.html

@@ -11,6 +11,7 @@
       computed-inline2="{{computeInline(value, add,divide)}}"
       computedattribute$="{{computeInline(value, add,divide)}}"
       neg-computed-inline="{{!computeInline(value,add,divide)}}"
+      computed-negative-number="{{computeNegativeNumber(-1)}}"
       style$="{{boundStyle}}"
       data-id$="{{dataSetId}}"
       custom-event-value="{{customEventValue::custom}}"
@@ -232,6 +233,9 @@
       },
       computeFromNoArgs: function() {
         return 'no args!';
+      },
+      computeNegativeNumber: function (num) {
+        return num;
       }
     });
   </script>