Send the AnnotationStorage-data to the worker-thread as a Map

Rather than converting the `AnnotationStorage`-data to an Object, before sending it to the worker-thread, we should be able to simply send the internal `Map` directly.
The "structured clone algorithm" doesn't have a problem with `Map`s, however the `LoopbackPort` used when workers are *disabled* (e.g. in Node.js environments) didn't use to support them. With PR 12997 having lifted that restriction, we should now be able to simply send the `AnnotationStorage`-data as-is rather than having to iterate through it to first create an Object.

*Please note:* The changes in `src/core/annotation.js` could have been a lot more compact if we were able to use optional chaining in the `src/core` folder. Unfortunately that's still not possible, since SystemJS is being used in the development viewer (i.g. `gulp server`) and fixing that is *still* blocked by [bug 1247687](https://bugzilla.mozilla.org/show_bug.cgi?id=1247687).

src/core/annotation.js

@@ -348,9 +348,10 @@ class Annotation {
   }
 
   isHidden(annotationStorage) {
-    const data = annotationStorage && annotationStorage[this.data.id];
-    if (data && "hidden" in data) {
-      return data.hidden;
+    const storageEntry =
+      annotationStorage && annotationStorage.get(this.data.id);
+    if (storageEntry && storageEntry.hidden !== undefined) {
+      return storageEntry.hidden;
     }
     return this._hasFlag(this.flags, AnnotationFlag.HIDDEN);
   }
@@ -1206,8 +1207,11 @@ class WidgetAnnotation extends Annotation {
   }
 
   async save(evaluator, task, annotationStorage) {
-    const value =
-      annotationStorage[this.data.id] && annotationStorage[this.data.id].value;
+    if (!annotationStorage) {
+      return null;
+    }
+    const storageEntry = annotationStorage.get(this.data.id);
+    const value = storageEntry && storageEntry.value;
     if (value === this.data.fieldValue || value === undefined) {
       return null;
     }
@@ -1289,8 +1293,8 @@ class WidgetAnnotation extends Annotation {
     if (!annotationStorage || isPassword) {
       return null;
     }
-    let value =
-      annotationStorage[this.data.id] && annotationStorage[this.data.id].value;
+    const storageEntry = annotationStorage.get(this.data.id);
+    let value = storageEntry && storageEntry.value;
     if (value === undefined) {
       // The annotation hasn't been rendered so use the appearance
       return null;
@@ -1769,9 +1773,8 @@ class ButtonWidgetAnnotation extends WidgetAnnotation {
     }
 
     if (annotationStorage) {
-      const value =
-        annotationStorage[this.data.id] &&
-        annotationStorage[this.data.id].value;
+      const storageEntry = annotationStorage.get(this.data.id);
+      const value = storageEntry && storageEntry.value;
       if (value === undefined) {
         return super.getOperatorList(
           evaluator,
@@ -1826,8 +1829,11 @@ class ButtonWidgetAnnotation extends WidgetAnnotation {
   }
 
   async _saveCheckbox(evaluator, task, annotationStorage) {
-    const value =
-      annotationStorage[this.data.id] && annotationStorage[this.data.id].value;
+    if (!annotationStorage) {
+      return null;
+    }
+    const storageEntry = annotationStorage.get(this.data.id);
+    const value = storageEntry && storageEntry.value;
     if (value === undefined) {
       return null;
     }
@@ -1869,8 +1875,11 @@ class ButtonWidgetAnnotation extends WidgetAnnotation {
   }
 
   async _saveRadioButton(evaluator, task, annotationStorage) {
-    const value =
-      annotationStorage[this.data.id] && annotationStorage[this.data.id].value;
+    if (!annotationStorage) {
+      return null;
+    }
+    const storageEntry = annotationStorage.get(this.data.id);
+    const value = storageEntry && storageEntry.value;
     if (value === undefined) {
       return null;
     }

src/display/annotation_storage.js

@@ -91,10 +91,7 @@ class AnnotationStorage {
   }
 
   getAll() {
-    if (this._storage.size === 0) {
-      return null;
-    }
-    return objectFromEntries(this._storage);
+    return this._storage.size > 0 ? objectFromEntries(this._storage) : null;
   }
 
   get size() {
@@ -121,6 +118,14 @@ class AnnotationStorage {
       }
     }
   }
+
+  /**
+   * PLEASE NOTE: Only intended for usage within the API itself.
+   * @ignore
+   */
+  get serializable() {
+    return this._storage.size > 0 ? this._storage : null;
+  }
 }
 
 export { AnnotationStorage };

src/display/api.js

@@ -1214,7 +1214,7 @@ class PDFPageProxy {
         pageIndex: this._pageIndex,
         intent: renderingIntent,
         renderInteractiveForms: renderInteractiveForms === true,
-        annotationStorage: annotationStorage?.getAll() || null,
+        annotationStorage: annotationStorage?.serializable || null,
       });
     }
 
@@ -2613,7 +2613,7 @@ class WorkerTransport {
     return this.messageHandler
       .sendWithPromise("SaveDocument", {
         numPages: this._numPages,
-        annotationStorage: annotationStorage?.getAll() || null,
+        annotationStorage: annotationStorage?.serializable || null,
         filename: this._fullReader?.filename ?? null,
       })
       .finally(() => {