fix: missing types on the scroll dispatcher

Author: crisbeto

src/lib/core/overlay/scroll/close-scroll-strategy.ts

@@ -11,7 +11,7 @@ export class CloseScrollStrategy implements ScrollStrategy {
   private _scrollSubscription: Subscription|null = null;
   private _overlayRef: OverlayRef;
 
-  constructor(private _scrollDispatcher) { }
+  constructor(private _scrollDispatcher: ScrollDispatcher) { }
 
   attach(overlayRef: OverlayRef) {
     this._overlayRef = overlayRef;

src/lib/core/overlay/scroll/reposition-scroll-strategy.ts

@@ -11,7 +11,7 @@ export class RepositionScrollStrategy implements ScrollStrategy {
   private _scrollSubscription: Subscription|null = null;
   private _overlayRef: OverlayRef;
 
-  constructor(private _scrollDispatcher, private _scrollThrottle = 0) { }
+  constructor(private _scrollDispatcher: ScrollDispatcher, private _scrollThrottle = 0) { }
 
   attach(overlayRef: OverlayRef) {
     this._overlayRef = overlayRef;