[api-minor] Add a basic AbortSignal.any polyfill in PDF.js legacy builds

This is an admittedly very basic polyfill, to allow us to remove a bunch of inline feature testing, that I've thrown together based on reading https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal/any_static and related MDN articles.

Compared to PR 19218 it's obviously much more "primitive", however the implementation is simple and it doesn't suffer from any licensing issues (since I wrote the code myself).

Author: Snuffleupagus

src/shared/util.js

@@ -1172,6 +1172,37 @@ if (
   };
 }
 
+if (
+  typeof PDFJSDev !== "undefined" &&
+  !PDFJSDev.test("SKIP_BABEL") &&
+  typeof AbortSignal.any !== "function"
+) {
+  AbortSignal.any = function (iterable) {
+    const ac = new AbortController();
+    const { signal } = ac;
+
+    // Return immediately if any of the signals are already aborted.
+    for (const s of iterable) {
+      if (s.aborted) {
+        ac.abort(s.reason);
+        return signal;
+      }
+    }
+    // Register "abort" listeners for all signals.
+    for (const s of iterable) {
+      s.addEventListener(
+        "abort",
+        () => {
+          ac.abort(s.reason);
+        },
+        { signal } // Automatically remove the listener.
+      );
+    }
+
+    return signal;
+  };
+}
+
 export {
   _isValidExplicitDest,
   AbortException,

web/app.js

@@ -559,11 +559,7 @@ const PDFViewerApplication = {
     }
 
     if (appConfig.annotationEditorParams) {
-      if (
-        ((typeof PDFJSDev !== "undefined" && PDFJSDev.test("MOZCENTRAL")) ||
-          typeof AbortSignal.any === "function") &&
-        annotationEditorMode !== AnnotationEditorType.DISABLE
-      ) {
+      if (annotationEditorMode !== AnnotationEditorType.DISABLE) {
         const editorSignatureButton = appConfig.toolbar?.editorSignatureButton;
         if (editorSignatureButton && AppOptions.get("enableSignatureEditor")) {
           editorSignatureButton.parentElement.hidden = false;
@@ -2075,19 +2071,14 @@ const PDFViewerApplication = {
       _windowAbortController: { signal },
     } = this;
 
-    if (
-      (typeof PDFJSDev !== "undefined" && PDFJSDev.test("MOZCENTRAL")) ||
-      typeof AbortSignal.any === "function"
-    ) {
-      this._touchManager = new TouchManager({
-        container: window,
-        isPinchingDisabled: () => pdfViewer.isInPresentationMode,
-        isPinchingStopped: () => this.overlayManager?.active,
-        onPinching: this.touchPinchCallback.bind(this),
-        onPinchEnd: this.touchPinchEndCallback.bind(this),
-        signal,
-      });
-    }
+    this._touchManager = new TouchManager({
+      container: window,
+      isPinchingDisabled: () => pdfViewer.isInPresentationMode,
+      isPinchingStopped: () => this.overlayManager?.active,
+      onPinching: this.touchPinchCallback.bind(this),
+      onPinchEnd: this.touchPinchEndCallback.bind(this),
+      signal,
+    });
 
     function addWindowResolutionChange(evt = null) {
       if (evt) {

web/pdf_viewer.js

@@ -711,13 +711,7 @@ class PDFViewer {
           hiddenCapability.resolve();
         }
       },
-      {
-        signal:
-          (typeof PDFJSDev !== "undefined" && PDFJSDev.test("MOZCENTRAL")) ||
-          typeof AbortSignal.any === "function"
-            ? AbortSignal.any([signal, ac.signal])
-            : signal,
-      }
+      { signal: AbortSignal.any([signal, ac.signal]) }
     );
 
     await Promise.race([
@@ -914,11 +908,7 @@ class PDFViewer {
           viewer.before(element);
         }
 
-        if (
-          ((typeof PDFJSDev !== "undefined" && PDFJSDev.test("MOZCENTRAL")) ||
-            typeof AbortSignal.any === "function") &&
-          annotationEditorMode !== AnnotationEditorType.DISABLE
-        ) {
+        if (annotationEditorMode !== AnnotationEditorType.DISABLE) {
           const mode = annotationEditorMode;
 
           if (pdfDocument.isPureXfa) {