[refactored] _debounce to use named args

Summary: Continuation of #193

Reviewers: O2 Material Motion, O3 Material JavaScript platform reviewers, #material_motion, featherless

Reviewed By: O2 Material Motion, #material_motion, featherless

Tags: #material_motion

Differential Revision: http://codereview.cc/D3399

packages/core/src/getFrame$.ts

@@ -29,7 +29,8 @@ import {
  *
  * Useful as a pulse for `_debounce` to ensure that UI work only happens once
  * per frame.  Since no rendering will happen until `requestAnimationFrame` is
- * called, it should be safe to `_debounce(frame$)` without missing a frame.
+ * called, it should be safe to `_debounce({ pulse$: frame$ })` without missing
+ * a frame.
  */
 let frame$: ObservableWithMotionOperators<number>;
 export function getFrame$() {

packages/core/src/interactions/Tossable.ts

@@ -168,10 +168,10 @@ export class Tossable {
     // start from 0
     subscribe({
       sink: spring.initialValue$,
-      source: this.location$._debounce(whenDragIsAtRest$)
+      source: this.location$._debounce({ pulse$: whenDragIsAtRest$}),
     });
 
-    const locationOnDown$ = this.location$._debounce(whenDragIsActive$);
+    const locationOnDown$ = this.location$._debounce({ pulse$: whenDragIsActive$ });
 
     this.draggedLocation$ = draggable.value$.addedBy<Point2D>(locationOnDown$, { onlyDispatchWithUpstream: true })._reactiveMap({
       transform: ({

packages/core/src/interactions/__tests__/Point2DSpring.test.ts

@@ -76,7 +76,7 @@ describe('Point2DSpring',
           //
           // Thus, we only measure what its values are when the state changes,
           // to be sure we are checking the correct values.
-          spring.value$._debounce(spring.state$).subscribe(valueListener);
+          spring.value$._debounce({ pulse$: spring.state$ }).subscribe(valueListener);
 
           const initialValue = { x: 2, y: 3 };
           const destination = { x: 4, y: 2 };
@@ -230,7 +230,7 @@ describe('Point2DSpring',
           //
           // Thus, we only measure what its values are when the state changes,
           // to be sure we are checking the correct values.
-          spring.value$._debounce(spring.state$).subscribe(valueListener);
+          spring.value$._debounce({ pulse$: spring.state$ }).subscribe(valueListener);
 
           const initialValue = { x: 4, y: 8 };
           const destination = { x: 0, y: 0 };

packages/core/src/operators/foundation/_debounce.ts

@@ -31,8 +31,12 @@ import {
   Observer
 } from '../../types';
 
+export type _DebounceArgs = {
+  pulse$?: Observable<any>,
+}
+
 export interface MotionDebounceable<T> {
-  _debounce(pulse$?: Observable<any>): ObservableWithMotionOperators<T>;
+  _debounce(kwargs?: _DebounceArgs): ObservableWithMotionOperators<T>;
 }
 
 export function withDebounce<T, S extends Constructor<MotionNextOperable<T>>>(superclass: S): S
@@ -47,7 +51,7 @@ export function withDebounce<T, S extends Constructor<MotionNextOperable<T>>>(su
      * By default, it will throttle to the framerate using
      * `requestAnimationFrame`.
      */
-    _debounce(pulse$: Observable<any> = getFrame$()): ObservableWithMotionOperators<T> {
+    _debounce({ pulse$ = getFrame$() } = {}): ObservableWithMotionOperators<T> {
       return new MotionObservable<T>(
         (observer: Observer<T>) => {
           let awaitingDispatch = false;