fix(core): fix decorator defalut values

modules/@angular/core/src/util/decorators.ts

@@ -297,21 +297,20 @@ export function makeDecorator(
 }
 
 function makeMetadataCtor(props: ([string, any] | {[key: string]: any})[]): any {
-  function ctor(...args: any[]) {
+  return function ctor(...args: any[]) {
     props.forEach((prop, i) => {
       const argVal = args[i];
       if (Array.isArray(prop)) {
         // plain parameter
-        this[prop[0]] = !argVal || argVal === undefined ? prop[1] : argVal;
+        this[prop[0]] = argVal === undefined ? prop[1] : argVal;
       } else {
-        for (let propName in prop) {
+        for (const propName in prop) {
           this[propName] =
-              !argVal || argVal[propName] === undefined ? prop[propName] : argVal[propName];
+              argVal && argVal.hasOwnProperty(propName) ? argVal[propName] : prop[propName];
         }
       }
     });
-  }
+  };
-  return ctor;
 }
 
 export function makeParamDecorator(

modules/@angular/core/test/util/decorators_spec.ts

@@ -35,6 +35,18 @@ export function main() {
       const p = reflector.propMetadata(TestClass);
       expect(p['watch']).toEqual([new Prop('firefox!')]);
     });
+
+    it('should work with any default plain values', () => {
+      const Default = makePropDecorator('Default', [['value', 5]]);
+      expect(new Default(0)['value']).toEqual(0);
+    });
+
+    it('should work with any object values', () => {
+      // make sure we don't walk up the prototype chain
+      const Default = makePropDecorator('Default', [{value: 5}]);
+      const value = Object.create({value: 10});
+      expect(new Default(value)['value']).toEqual(5);
+    });
   });
 
   describe('decorators', () => {