[api-minor] Initialize the unicode-category *lazily* on the Glyph-instance

The purpose of this patch is twofold:
 - Initialize the unicode-category data *lazily* during text-extraction, since this is completely unused during general parsing/rendering.
 - Stop exposing this data in the API, since it's unused on the main-thread and it seems like it was *accidentally* included.

Obviously these changes are API-observable, but hopefully no user is depending on this. Furthermore, it's trivial for a user to re-create this unicode-category data manually with a regular expression (from the exposed `unicode` property).

src/core/evaluator.js

@@ -2775,7 +2775,9 @@ class PartialEvaluator {
 
       for (let i = 0, ii = glyphs.length; i < ii; i++) {
         const glyph = glyphs[i];
-        if (glyph.isInvisibleFormatMark) {
+        const { category } = glyph;
+
+        if (category.isInvisibleFormatMark) {
           continue;
         }
         let charSpacing =
@@ -2787,7 +2789,7 @@ class PartialEvaluator {
         }
         let scaledDim = glyphWidth * scale;
 
-        if (glyph.isWhitespace) {
+        if (category.isWhitespace) {
           // Don't push a " " in the textContentItem
           // (except when it's between two non-spaces chars),
           // it will be done (if required) in next call to
@@ -2815,7 +2817,7 @@ class PartialEvaluator {
         // Must be called after compareWithLastPosition because
         // the textContentItem could have been flushed.
         const textChunk = ensureTextContentItem();
-        if (glyph.isZeroWidthDiacritic) {
+        if (category.isZeroWidthDiacritic) {
           scaledDim = 0;
         }
 

src/core/fonts.js

@@ -214,11 +214,20 @@ class Glyph {
     this.operatorListId = operatorListId;
     this.isSpace = isSpace;
     this.isInFont = isInFont;
+  }
 
-    const category = getCharUnicodeCategory(unicode);
-    this.isWhitespace = category.isWhitespace;
-    this.isZeroWidthDiacritic = category.isZeroWidthDiacritic;
-    this.isInvisibleFormatMark = category.isInvisibleFormatMark;
+  /**
+   * This property, which is only used by `PartialEvaluator.getTextContent`,
+   * is purposely made non-serializable.
+   * @type {Object}
+   */
+  get category() {
+    return shadow(
+      this,
+      "category",
+      getCharUnicodeCategory(this.unicode),
+      /* nonSerializable = */ true
+    );
   }
 
   /**