change function to private

Author: sllethe

src/lib/list/selection-list.ts

@@ -86,8 +86,8 @@ export class MdSelectionList extends _MdSelectionListMixinBase
       this._tabIndex = -1;
     }
 
-    this._optionFocusSubscription = this.onFocusSubscription();
-    this._optionDestroyStream = this.onDestroySubscription();
+    this._optionFocusSubscription = this._onFocusSubscription();
+    this._optionDestroyStream = this._onDestroySubscription();
   }
 
   ngOnDestroy(): void {
@@ -107,7 +107,7 @@ export class MdSelectionList extends _MdSelectionListMixinBase
   /**
    * Map all the options' destroy event subscriptions and merge them into one stream.
    */
-  onDestroySubscription(): Subscription {
+  private _onDestroySubscription(): Subscription {
     return RxChain.from(this.options.changes)
       .call(startWith, this.options)
       .call(switchMap, (options: MdListOption[]) => {
@@ -129,7 +129,7 @@ export class MdSelectionList extends _MdSelectionListMixinBase
   /**
    * Map all the options' onFocus event subscriptions and merge them into one stream.
    */
-  onFocusSubscription(): Subscription {
+  private _onFocusSubscription(): Subscription {
     return RxChain.from(this.options.changes)
       .call(startWith, this.options)
       .call(switchMap, (options: MdListOption[]) => {