Attach (recommended) or Link to PDF file here:

Configuration:
- Web browser and its version: Chrome 63.0.3239.132 
- Operating system and its version: Windows 10
- PDF.js version: using your official demo project
- Is a browser extension: No

Steps to reproduce the problem:
1.  Just load attached pdf
2.

What is the expected behavior? (add screenshot)
[E-WG18_105147.pdf](https://github.com/mozilla/pdf.js/files/1634833/E-WG18_105147.pdf)

What went wrong? (add screenshot)
![image](https://user-images.githubusercontent.com/29802177/34986271-3ca71a5c-fab7-11e7-95e8-1739dda3cd04.png)

Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension):

const map = [];
      this.toUnicode.forEach((charCode, unicodeCharCode) => {
        if (!this.composite) {
          const glyphName =
            this.differences[charCode] || this.defaultEncoding[charCode];
          const unicode = getUnicodeForGlyph(glyphName, glyphsUnicodeMap);
          if (unicode !== -1) {
            unicodeCharCode = unicode;
          }
        }
        map[+charCode] = unicodeCharCode;
      });
      
      
      if (this.composite && this.toUnicode instanceof IdentityToUnicodeMap) {
        if (/Verdana/i.test(name)) {
          
          const GlyphMapForStandardFonts = getGlyphMapForStandardFonts();
          for (const charCode in GlyphMapForStandardFonts) {
            map[+charCode] = GlyphMapForStandardFonts[charCode];
          }
        }
      }
      this.toFontChar = map;
    }
    amendFallbackToUnicode(properties);
    this.loadedName = fontName.split("-")[0];
    this.fontType = getFontType(type, subtype, properties.isStandardFont);
  }
  checkAndRepair(name, font, properties) {