fix(checkbox): not being marked as checked with ng-checked on load (#9424)

Fixes the checkbox not getting marked as checked on the first load when using `ng-checked`.

Fixes #9349

Author: crisbeto

src/components/checkbox/checkbox.js

@@ -109,10 +109,10 @@ function MdCheckboxDirective(inputDirective, $mdAria, $mdConstant, $mdTheming, $
       }
 
       if (attr.ngChecked) {
-        scope.$watch(
-          scope.$eval.bind(scope, attr.ngChecked),
-          ngModelCtrl.$setViewValue.bind(ngModelCtrl)
-        );
+        scope.$watch(scope.$eval.bind(scope, attr.ngChecked), function(value) {
+          ngModelCtrl.$setViewValue(value);
+          ngModelCtrl.$render();
+        });
       }
 
       $$watchExpr('ngDisabled', 'tabindex', {

src/components/checkbox/checkbox.spec.js

@@ -254,6 +254,14 @@ describe('mdCheckbox', function() {
       expect(checkbox.hasClass(CHECKED_CSS)).toBe(false);
     });
 
+    it('should mark the checkbox as selected on load with ng-checked', function() {
+      pageScope.isChecked = function() { return true; };
+
+      var checkbox = compileAndLink('<md-checkbox ng-model="checked" ng-checked="isChecked()"></md-checkbox>');
+
+      expect(checkbox).toHaveClass(CHECKED_CSS);
+    });
+
     describe('with the md-indeterminate attribute', function() {
 
       it('should set md-indeterminate attr to true by default', function() {