Convert FontFaceObject to an ES6 class

Also changes `var` to `let`/`const` in code already touched in the patch, and makes use of template strings in a few spots.

src/display/font_loader.js

@@ -330,21 +330,21 @@ if (typeof PDFJSDev === 'undefined' || !PDFJSDev.test('MOZCENTRAL || CHROME')) {
   });
 }
 
-var IsEvalSupportedCached = {
+const IsEvalSupportedCached = {
   get value() {
     return shadow(this, 'value', isEvalSupported());
   },
 };
 
-var FontFaceObject = (function FontFaceObjectClosure() {
+class FontFaceObject {
-  function FontFaceObject(translatedData, { isEvalSupported = true,
+  constructor(translatedData, { isEvalSupported = true,
-                                            disableFontFace = false,
+                                disableFontFace = false,
-                                            ignoreErrors = false,
+                                ignoreErrors = false,
-                                            onUnsupportedFeature = null,
+                                onUnsupportedFeature = null,
-                                            fontRegistry = null, }) {
+                                fontRegistry = null, }) {
     this.compiledGlyphs = Object.create(null);
     // importing translated data
-    for (var i in translatedData) {
+    for (let i in translatedData) {
       this[i] = translatedData[i];
     }
     this.isEvalSupported = isEvalSupported !== false;
@@ -353,98 +353,86 @@ var FontFaceObject = (function FontFaceObjectClosure() {
     this._onUnsupportedFeature = onUnsupportedFeature;
     this.fontRegistry = fontRegistry;
   }
-  FontFaceObject.prototype = {
+
-    createNativeFontFace: function FontFaceObject_createNativeFontFace() {
+  createNativeFontFace() {
-      if (typeof PDFJSDev !== 'undefined' && PDFJSDev.test('MOZCENTRAL')) {
+    if (!this.data || this.disableFontFace) {
-        throw new Error('Not implemented: createNativeFontFace');
+      return null;
+    }
+    const nativeFontFace = new FontFace(this.loadedName, this.data, {});
+
+    if (this.fontRegistry) {
+      this.fontRegistry.registerFont(this);
+    }
+    return nativeFontFace;
+  }
+
+  createFontFaceRule() {
+    if (!this.data || this.disableFontFace) {
+      return null;
+    }
+    const data = bytesToString(new Uint8Array(this.data));
+    // Add the @font-face rule to the document.
+    const url = `url(data:${this.mimetype};base64,${btoa(data)});`;
+    const rule = `@font-face {font-family:"${this.loadedName}";src:${url}}`;
+
+    if (this.fontRegistry) {
+      this.fontRegistry.registerFont(this, url);
+    }
+    return rule;
+  }
+
+  getPathGenerator(objs, character) {
+    if (this.compiledGlyphs[character] !== undefined) {
+      return this.compiledGlyphs[character];
+    }
+
+    let cmds, current;
+    try {
+      cmds = objs.get(this.loadedName + '_path_' + character);
+    } catch (ex) {
+      if (!this.ignoreErrors) {
+        throw ex;
       }
-
+      if (this._onUnsupportedFeature) {
-      if (!this.data || this.disableFontFace) {
+        this._onUnsupportedFeature({ featureId: UNSUPPORTED_FEATURES.font, });
-        return null;
       }
+      warn(`getPathGenerator - ignoring character: "${ex}".`);
 
-      var nativeFontFace = new FontFace(this.loadedName, this.data, {});
-
-      if (this.fontRegistry) {
-        this.fontRegistry.registerFont(this);
-      }
-      return nativeFontFace;
-    },
-
-    createFontFaceRule: function FontFaceObject_createFontFaceRule() {
-      if (!this.data || this.disableFontFace) {
-        return null;
-      }
-
-      var data = bytesToString(new Uint8Array(this.data));
-      var fontName = this.loadedName;
-
-      // Add the font-face rule to the document
-      var url = ('url(data:' + this.mimetype + ';base64,' + btoa(data) + ');');
-      var rule = '@font-face { font-family:"' + fontName + '";src:' + url + '}';
-
-      if (this.fontRegistry) {
-        this.fontRegistry.registerFont(this, url);
-      }
-
-      return rule;
-    },
-
-    getPathGenerator(objs, character) {
-      if (this.compiledGlyphs[character] !== undefined) {
-        return this.compiledGlyphs[character];
-      }
-
-      let cmds, current;
-      try {
-        cmds = objs.get(this.loadedName + '_path_' + character);
-      } catch (ex) {
-        if (!this.ignoreErrors) {
-          throw ex;
-        }
-        if (this._onUnsupportedFeature) {
-          this._onUnsupportedFeature({ featureId: UNSUPPORTED_FEATURES.font, });
-        }
-        warn(`getPathGenerator - ignoring character: "${ex}".`);
-
-        return this.compiledGlyphs[character] = function(c, size) {
-          // No-op function, to allow rendering to continue.
-        };
-      }
-
-      // If we can, compile cmds into JS for MAXIMUM SPEED...
-      if (this.isEvalSupported && IsEvalSupportedCached.value) {
-        let args, js = '';
-        for (let i = 0, ii = cmds.length; i < ii; i++) {
-          current = cmds[i];
-
-          if (current.args !== undefined) {
-            args = current.args.join(',');
-          } else {
-            args = '';
-          }
-          js += 'c.' + current.cmd + '(' + args + ');\n';
-        }
-        // eslint-disable-next-line no-new-func
-        return this.compiledGlyphs[character] = new Function('c', 'size', js);
-      }
-      // ... but fall back on using Function.prototype.apply() if we're
-      // blocked from using eval() for whatever reason (like CSP policies).
       return this.compiledGlyphs[character] = function(c, size) {
-        for (let i = 0, ii = cmds.length; i < ii; i++) {
+        // No-op function, to allow rendering to continue.
-          current = cmds[i];
-
-          if (current.cmd === 'scale') {
-            current.args = [size, -size];
-          }
-          c[current.cmd].apply(c, current.args);
-        }
       };
-    },
+    }
-  };
 
-  return FontFaceObject;
+    // If we can, compile cmds into JS for MAXIMUM SPEED...
-})();
+    if (this.isEvalSupported && IsEvalSupportedCached.value) {
+      let args, js = '';
+      for (let i = 0, ii = cmds.length; i < ii; i++) {
+        current = cmds[i];
+
+        if (current.args !== undefined) {
+          args = current.args.join(',');
+        } else {
+          args = '';
+        }
+        js += 'c.' + current.cmd + '(' + args + ');\n';
+      }
+      // eslint-disable-next-line no-new-func
+      return this.compiledGlyphs[character] = new Function('c', 'size', js);
+    }
+    // ... but fall back on using Function.prototype.apply() if we're
+    // blocked from using eval() for whatever reason (like CSP policies).
+    return this.compiledGlyphs[character] = function(c, size) {
+      for (let i = 0, ii = cmds.length; i < ii; i++) {
+        current = cmds[i];
+
+        if (current.cmd === 'scale') {
+          current.args = [size, -size];
+        }
+        c[current.cmd].apply(c, current.args);
+      }
+    };
+  }
+}
 
 export {
   FontFaceObject,