[api-minor] Replace the PromiseCapability with Promise.withResolvers()

This replaces our custom `PromiseCapability`-class with the new native `Promise.withResolvers()` functionality, which does *almost* the same thing[1]; please see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/withResolvers

The only difference is that `PromiseCapability` also had a `settled`-getter, which was however not widely used and the call-sites can either be removed or re-factored to avoid it. In particular:
 - In `src/display/api.js` we can tweak the `PDFObjects`-class to use a "special" initial data-value and just compare against that, in order to replace the `settled`-state.
 - In `web/app.js` we change the only case to manually track the `settled`-state, which should hopefully be OK given how this is being used.
 - In `web/pdf_outline_viewer.js` we can remove the `settled`-checks, since the code should work just fine without it. The only thing that could potentially happen is that we try to `resolve` a Promise multiple times, which is however *not* a problem since the value of a Promise cannot be changed once fulfilled or rejected.
 - In `web/pdf_viewer.js` we can remove the `settled`-checks, since the code should work fine without them:
     - For the `_onePageRenderedCapability` case the `settled`-check is used in a `EventBus`-listener which is *removed* on its first (valid) invocation.
     - For the `_pagesCapability` case the `settled`-check is used in a print-related helper that works just fine with "only" the other checks.
 - In `test/unit/api_spec.js` we can change the few relevant cases to manually track the `settled`-state, since this is both simple and *test-only* code.

---
[1] In browsers/environments that lack native support, note [the compatibility data](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/withResolvers#browser_compatibility), it'll be polyfilled via the `core-js` library (but only in `legacy` builds).

test/driver.js

@@ -22,7 +22,6 @@ const {
   GlobalWorkerOptions,
   Outliner,
   PixelsPerInch,
-  PromiseCapability,
   renderTextLayer,
   shadow,
   XfaLayer,
@@ -1112,7 +1111,7 @@ class Driver {
   }
 
   _send(url, message) {
-    const capability = new PromiseCapability();
+    const { promise, resolve } = Promise.withResolvers();
     this.inflight.textContent = this.inFlightRequests++;
 
     fetch(url, {
@@ -1129,18 +1128,18 @@ class Driver {
         }
 
         this.inFlightRequests--;
-        capability.resolve();
+        resolve();
       })
       .catch(reason => {
         console.warn(`Driver._send failed (${url}): ${reason}`);
 
         this.inFlightRequests--;
-        capability.resolve();
+        resolve();
 
         this._send(url, message);
       });
 
-    return capability.promise;
+    return promise;
   }
 }
 

test/unit/api_spec.js

@@ -26,7 +26,6 @@ import {
   PasswordException,
   PasswordResponses,
   PermissionFlag,
-  PromiseCapability,
   UnknownErrorException,
 } from "../../src/shared/util.js";
 import {
@@ -156,13 +155,11 @@ describe("api", function () {
       const loadingTask = getDocument(basicApiGetDocumentParams);
       expect(loadingTask instanceof PDFDocumentLoadingTask).toEqual(true);
 
-      const progressReportedCapability = new PromiseCapability();
+      const progressReportedCapability = Promise.withResolvers();
       // Attach the callback that is used to report loading progress;
       // similarly to how viewer.js works.
       loadingTask.onProgress = function (progressData) {
-        if (!progressReportedCapability.settled) {
-          progressReportedCapability.resolve(progressData);
-        }
+        progressReportedCapability.resolve(progressData);
       };
 
       const data = await Promise.all([
@@ -218,7 +215,7 @@ describe("api", function () {
       const loadingTask = getDocument(typedArrayPdf);
       expect(loadingTask instanceof PDFDocumentLoadingTask).toEqual(true);
 
-      const progressReportedCapability = new PromiseCapability();
+      const progressReportedCapability = Promise.withResolvers();
       loadingTask.onProgress = function (data) {
         progressReportedCapability.resolve(data);
       };
@@ -248,7 +245,7 @@ describe("api", function () {
       const loadingTask = getDocument(arrayBufferPdf);
       expect(loadingTask instanceof PDFDocumentLoadingTask).toEqual(true);
 
-      const progressReportedCapability = new PromiseCapability();
+      const progressReportedCapability = Promise.withResolvers();
       loadingTask.onProgress = function (data) {
         progressReportedCapability.resolve(data);
       };
@@ -306,8 +303,14 @@ describe("api", function () {
       const loadingTask = getDocument(buildGetDocumentParams("pr6531_1.pdf"));
       expect(loadingTask instanceof PDFDocumentLoadingTask).toEqual(true);
 
-      const passwordNeededCapability = new PromiseCapability();
-      const passwordIncorrectCapability = new PromiseCapability();
+      const passwordNeededCapability = {
+        ...Promise.withResolvers(),
+        settled: false,
+      };
+      const passwordIncorrectCapability = {
+        ...Promise.withResolvers(),
+        settled: false,
+      };
       // Attach the callback that is used to request a password;
       // similarly to how the default viewer handles passwords.
       loadingTask.onPassword = function (updatePassword, reason) {
@@ -315,6 +318,7 @@ describe("api", function () {
           reason === PasswordResponses.NEED_PASSWORD &&
           !passwordNeededCapability.settled
         ) {
+          passwordNeededCapability.settled = true;
           passwordNeededCapability.resolve();
 
           updatePassword("qwerty"); // Provide an incorrect password.
@@ -324,6 +328,7 @@ describe("api", function () {
           reason === PasswordResponses.INCORRECT_PASSWORD &&
           !passwordIncorrectCapability.settled
         ) {
+          passwordIncorrectCapability.settled = true;
           passwordIncorrectCapability.resolve();
 
           updatePassword("asdfasdf"); // Provide the correct password.

test/unit/message_handler_spec.js

@@ -15,7 +15,6 @@
 
 import {
   AbortException,
-  PromiseCapability,
   UnknownErrorException,
 } from "../../src/shared/util.js";
 import { LoopbackPort } from "../../src/display/api.js";
@@ -336,7 +335,7 @@ describe("message_handler", function () {
     it("should ignore any pull after close is called", async function () {
       let log = "";
       const port = new LoopbackPort();
-      const capability = new PromiseCapability();
+      const { promise, resolve } = Promise.withResolvers();
       const messageHandler2 = new MessageHandler("worker", "main", port);
       messageHandler2.on("fakeHandler", (data, sink) => {
         sink.onPull = function () {
@@ -350,7 +349,7 @@ describe("message_handler", function () {
           log += "1";
           sink.enqueue([1, 2, 3, 4], 4);
         });
-        return capability.promise.then(() => {
+        return promise.then(() => {
           sink.close();
         });
       });
@@ -371,8 +370,8 @@ describe("message_handler", function () {
       await sleep(10);
       expect(log).toEqual("01");
 
-      capability.resolve();
-      await capability.promise;
+      resolve();
+      await promise;
 
       let result = await reader.read();
       expect(result.value).toEqual([1, 2, 3, 4]);

test/unit/pdf_spec.js

@@ -29,7 +29,6 @@ import {
   OPS,
   PasswordResponses,
   PermissionFlag,
-  PromiseCapability,
   shadow,
   UnexpectedResponseException,
   Util,
@@ -105,7 +104,6 @@ const expectedAPI = Object.freeze({
   PDFWorker,
   PermissionFlag,
   PixelsPerInch,
-  PromiseCapability,
   RenderingCancelledException,
   renderTextLayer,
   setLayerDimensions,

test/unit/util_spec.js

@@ -17,7 +17,6 @@ import {
   bytesToString,
   createValidAbsoluteUrl,
   getModificationDate,
-  PromiseCapability,
   string32,
   stringToBytes,
   stringToPDFString,
@@ -223,37 +222,6 @@ describe("util", function () {
     });
   });
 
-  describe("PromiseCapability", function () {
-    it("should resolve with correct data", async function () {
-      const promiseCapability = new PromiseCapability();
-      expect(promiseCapability.settled).toEqual(false);
-
-      promiseCapability.resolve({ test: "abc" });
-
-      const data = await promiseCapability.promise;
-      expect(promiseCapability.settled).toEqual(true);
-      expect(data).toEqual({ test: "abc" });
-    });
-
-    it("should reject with correct reason", async function () {
-      const promiseCapability = new PromiseCapability();
-      expect(promiseCapability.settled).toEqual(false);
-
-      promiseCapability.reject(new Error("reason"));
-
-      try {
-        await promiseCapability.promise;
-
-        // Shouldn't get here.
-        expect(false).toEqual(true);
-      } catch (reason) {
-        expect(promiseCapability.settled).toEqual(true);
-        expect(reason instanceof Error).toEqual(true);
-        expect(reason.message).toEqual("reason");
-      }
-    });
-  });
-
   describe("getModificationDate", function () {
     it("should get a correctly formatted date", function () {
       const date = new Date(Date.UTC(3141, 5, 9, 2, 6, 53));