refact(filter): move hasCustomToString into shared namespace to be reused

Author: petebacondarwin

src/.jshintrc

@@ -55,6 +55,7 @@
     "isBlob": false,
     "isBoolean": false,
     "isPromiseLike": false,
+    "hasCustomToString": false,
     "trim": false,
     "escapeForRegexp": false,
     "isElement": false,

src/Angular.js

@@ -464,6 +464,11 @@ identity.$inject = [];
 
 function valueFn(value) {return function() {return value;};}
 
+function hasCustomToString(obj) {
+  return isFunction(obj.toString) && obj.toString !== Object.prototype.toString;
+}
+
+
 /**
  * @ngdoc function
  * @name angular.isUndefined

src/ng/filter/filter.js

@@ -163,10 +163,6 @@ function filterFilter() {
   };
 }
 
-function hasCustomToString(obj) {
-  return isFunction(obj.toString) && obj.toString !== Object.prototype.toString;
-}
-
 // Helper functions for `filterFilter`
 function createPredicateFn(expression, comparator, matchAgainstAnyProp) {
   var shouldMatchPrimitives = isObject(expression) && ('$' in expression);