fix(ngc): _onDragStart/End are called with one param

Fixes #1112

Author: alexeagle

src/lib/slide-toggle/slide-toggle.ts

@@ -213,7 +213,7 @@ export class MdSlideToggle implements AfterContentInit, ControlValueAccessor {
 
 
   /** TODO: internal */
-  _onDragStart() {
+  _onDragStart(event: Event) {
     this._slideRenderer.startThumbDrag(this.checked);
   }
 
@@ -223,7 +223,7 @@ export class MdSlideToggle implements AfterContentInit, ControlValueAccessor {
   }
 
   /** TODO: internal */
-  _onDragEnd() {
+  _onDragEnd(event: Event) {
     // Notice that we have to stop outside of the current event handler,
     // because otherwise the click event will be fired and will reset the new checked variable.
     setTimeout(() => {