Implement creation date only for markup annotations

The specification states that `CreationDate` is only available for
markup annotations instead of for all annotation types.

(Note that the creation date logic is still tested in e.g. the popup
annotation unit tests, even though the generic setter is now removed.)

src/core/annotation.js

@@ -176,7 +176,6 @@ class Annotation {
     const dict = params.dict;
 
     this.setContents(dict.get('Contents'));
-    this.setCreationDate(dict.get('CreationDate'));
     this.setModificationDate(dict.get('M'));
     this.setFlags(dict.get('F'));
     this.setRectangle(dict.getArray('Rect'));
@@ -190,7 +189,6 @@ class Annotation {
       borderStyle: this.borderStyle,
       color: this.color,
       contents: this.contents,
-      creationDate: this.creationDate,
       hasAppearance: !!this.appearance,
       id: params.id,
       modificationDate: this.modificationDate,
@@ -257,18 +255,6 @@ class Annotation {
     this.contents = stringToPDFString(contents || '');
   }
 
-  /**
-   * Set the creation date.
-   *
-   * @public
-   * @memberof Annotation
-   * @param {string} creationDate - PDF date string that indicates when the
-   *                                annotation was originally created
-   */
-  setCreationDate(creationDate) {
-    this.creationDate = isString(creationDate) ? creationDate : null;
-  }
-
   /**
    * Set the modification date.
    *
@@ -629,13 +615,16 @@ class AnnotationBorderStyle {
 class MarkupAnnotation extends Annotation {
   constructor(parameters) {
     super(parameters);
-    const dict = parameters.dict;
 
+    const dict = parameters.dict;
     if (!dict.has('C')) {
       // Fall back to the default background color.
       this.data.color = null;
     }
 
+    const creationDate = dict.get('CreationDate');
+    this.data.creationDate = isString(creationDate) ? creationDate : null;
+
     this.data.hasPopup = dict.has('Popup');
     this.data.title = stringToPDFString(dict.get('T') || '');
   }
@@ -989,12 +978,8 @@ class PopupAnnotation extends Annotation {
     this.data.title = stringToPDFString(parentItem.get('T') || '');
     this.data.contents = stringToPDFString(parentItem.get('Contents') || '');
 
-    if (!parentItem.has('CreationDate')) {
-      this.data.creationDate = null;
-    } else {
-      this.setCreationDate(parentItem.get('CreationDate'));
-      this.data.creationDate = this.creationDate;
-    }
+    const creationDate = parentItem.get('CreationDate');
+    this.data.creationDate = isString(creationDate) ? creationDate : null;
 
     if (!parentItem.has('M')) {
       this.data.modificationDate = null;

test/unit/annotation_spec.js

@@ -145,28 +145,14 @@ describe('annotation', function() {
       expect(annotation.contents).toEqual('');
     });
 
-    it('should set and get a valid creation date', function() {
-      const annotation = new Annotation({ dict, ref, });
-      annotation.setCreationDate('D:20190422');
-
-      expect(annotation.creationDate).toEqual('D:20190422');
-    });
-
-    it('should set and get an invalid creation date', function() {
-      const annotation = new Annotation({ dict, ref, });
-      annotation.setCreationDate(undefined);
-
-      expect(annotation.creationDate).toEqual(null);
-    });
-
     it('should set and get a valid modification date', function() {
       const annotation = new Annotation({ dict, ref, });
       annotation.setModificationDate('D:20190422');
 
       expect(annotation.modificationDate).toEqual('D:20190422');
     });
 
-    it('should set and get an invalid modification date', function() {
+    it('should not set and get an invalid modification date', function() {
       const annotation = new Annotation({ dict, ref, });
       annotation.setModificationDate(undefined);