fix(ngModel): prevent internal scope reference from being copied

Fixes #15833

Author: jbedard

karma-shared.conf.js

@@ -6,7 +6,7 @@ module.exports = function(config, specificOptions) {
     autoWatch: true,
     logLevel: config.LOG_INFO,
     logColors: true,
-    browsers: ['Chrome'],
+    browsers: ['ChromeCanary'],
     browserDisconnectTimeout: 10000,
     browserDisconnectTolerance: 2,
     browserNoActivityTimeout: 30000,

src/ng/directive/ngModel.js

@@ -281,7 +281,9 @@ function NgModelController($scope, $exceptionHandler, $attr, $element, $parse, $
 
   this.$$currentValidationRunId = 0;
 
-  this.$$scope = $scope;
+  //https://github.com/angular/angular.js/issues/15833
+  //Prevent `$$scope` from being iterated over by `copy` when NgModelController is deep watched
+  Object.defineProperty(this, '$$scope', {value: $scope});
   this.$$attr = $attr;
   this.$$element = $element;
   this.$$animate = $animate;