CCA: Use WaitableEvent as session type in view.js

Bug: 1122444
Test: tast run <DUT> "camera.CCAUI*"
Change-Id: Ia6c99c524569a027cc52b38ce7bf24e2c8469f88
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2379425
Auto-Submit: Inker Kuo <inker@chromium.org>
Commit-Queue: Shik Chen <shik@chromium.org>
Reviewed-by: Shik Chen <shik@chromium.org>
Cr-Commit-Position: refs/heads/master@{#803807}

chromeos/components/camera_app_ui/resources/src/js/views/view.js

@@ -4,6 +4,7 @@
 
 import * as dom from '../dom.js';
 import {ViewName} from '../type.js';  // eslint-disable-line no-unused-vars
+import {WaitableEvent} from '../waitable_event.js';
 
 /* eslint-disable no-unused-vars */
 
@@ -54,7 +55,8 @@ export class View {
     this.rootElement_ = dom.get(`#${name}`, HTMLElement);
 
     /**
-     * @type {?Promise}
+     * Signal it to ends the session.
+     * @type {?WaitableEvent<*>}
      * @private
      */
     this.session_ = null;
@@ -131,17 +133,11 @@ export class View {
   enter(options) {
     // The session is started by entering the view and ended by leaving the
     // view.
-    if (!this.session_) {
-      let end;
-      this.session_ = new Promise((resolve) => {
-        end = resolve;
-      });
-      this.session_.end = (result) => {
-        end(result);
-      };
+    if (this.session_ === null) {
+      this.session_ = new WaitableEvent();
     }
     this.entering(options);
-    return this.session_;
+    return this.session_.wait();
   }
 
   /**
@@ -160,8 +156,8 @@ export class View {
    * @return {boolean} Whether able to leaving the view or not.
    */
   leave(condition) {
-    if (this.session_ && this.leaving(condition)) {
-      this.session_.end(condition);
+    if (this.session_ !== null && this.leaving(condition)) {
+      this.session_.signal(condition);
       this.session_ = null;
       return true;
     }

chromeos/components/camera_app_ui/resources/src/js/waitable_event.js

@@ -4,6 +4,7 @@
 
 /**
  * A waitable event for synchronization between asynchronous jobs.
+ * @template T
  */
 export class WaitableEvent {
   /**
@@ -17,13 +18,13 @@ export class WaitableEvent {
     this.isSignaled_ = false;
 
     /**
-     * @type {function(): void}
+     * @type {function(T): void}
      * @private
      */
     this.resolve_;
 
     /**
-     * @type {!Promise}
+     * @type {!Promise<T>}
      * @private
      */
     this.promise_ = new Promise((resolve) => {
@@ -40,19 +41,20 @@ export class WaitableEvent {
 
   /**
    * Signals the event.
+   * @param {T=} value
    */
-  signal() {
+  signal(value) {
     if (this.isSignaled_) {
       return;
     }
     this.isSignaled_ = true;
-    this.resolve_();
+    this.resolve_(value);
   }
 
   /**
-   * @return {!Promise} Resolved when the event is signaled.
+   * @return {!Promise<T>} Resolved when the event is signaled.
    */
-  async wait() {
-    await this.promise_;
+  wait() {
+    return this.promise_;
   }
 }