Addressed comments

Author: tinayuangao

src/lib/radio/radio.html

@@ -6,7 +6,7 @@
   <div class="md-radio-container">
     <div class="md-radio-outer-circle"></div>
     <div class="md-radio-inner-circle"></div>
-    <div md-ripple *ngIf="isRippleEnabled()" class="md-radio-ripple"
+    <div md-ripple *ngIf="!disableRipple" class="md-radio-ripple"
          [md-ripple-trigger]="getHostElement()"
          [md-ripple-centered]="true"
          [md-ripple-speed-factor]="0.3"

src/lib/radio/radio.spec.ts

@@ -221,14 +221,16 @@ describe('MdRadio', () => {
       fixture.detectChanges();
       for (let radioNativeElement of radioNativeElements)
       {
-        expect(radioNativeElement.querySelectorAll('[md-ripple]').length).toBe(1);
+        expect(radioNativeElement.querySelectorAll('[md-ripple]').length)
+          .toBe(1, 'Expect [md-ripple] in radio buttons');
       }
 
       testComponent.disableRipple = true;
       fixture.detectChanges();
       for (let radioNativeElement of radioNativeElements)
       {
-        expect(radioNativeElement.querySelectorAll('[md-ripple]').length).toBe(0);
+        expect(radioNativeElement.querySelectorAll('[md-ripple]').length)
+          .toBe(0, 'Expect no [md-ripple] in radio buttons');
       }
     }));
   });

src/lib/radio/radio.ts

@@ -421,10 +421,6 @@ export class MdRadioButton implements OnInit {
   getHostElement() {
     return this._elementRef.nativeElement;
   }
-
-  isRippleEnabled() {
-    return !this.disableRipple;
-  }
 }