fixed group ripple disabled test

Author: tinayuangao

src/lib/radio/radio.spec.ts

@@ -595,7 +595,8 @@ describe('MdRadio', () => {
                   [labelPosition]="labelPos"
                   [value]="groupValue"
                   name="test-name">
-    <md-radio-button value="fire" [disableRipple]="disableRipple">Charmander</md-radio-button>
+    <md-radio-button value="fire" [disableRipple]="disableRipple"
+                     [disabled]="isFirstDisabled">Charmander</md-radio-button>
     <md-radio-button value="water" [disableRipple]="disableRipple">Squirtle</md-radio-button>
     <md-radio-button value="leaf" [disableRipple]="disableRipple">Bulbasaur</md-radio-button>
   </md-radio-group>
@@ -604,6 +605,7 @@ describe('MdRadio', () => {
 class RadiosInsideRadioGroup {
   labelPos: 'before' | 'after';
   isGroupDisabled: boolean = false;
+  isFirstDisabled: boolean = false;
   groupValue: string = null;
   disableRipple: boolean = false;
 }

src/lib/radio/radio.ts

@@ -144,7 +144,7 @@ export class MdRadioGroup extends _MdRadioGroupMixinBase
   set labelPosition(v) {
     this._labelPosition = (v == 'before') ? 'before' : 'after';
     if (this._radios) {
-      this._radios.forEach(radio => radio.groupValueChanged());
+      this._radios.forEach(radio => radio._groupValueChanged());
     }
   }
 
@@ -480,7 +480,7 @@ export class MdRadioButton implements OnInit, AfterViewInit, OnDestroy {
     this._focusOriginMonitor.focusVia(this._inputElement.nativeElement, this._renderer, 'keyboard');
   }
 
-  groupValueChanged() {
+  _groupValueChanged() {
     this._changeDetector.markForCheck();
   }