Attach (recommended) or Link to PDF file here:
[chinese.pdf](https://github.com/mozilla/pdf.js/files/6404389/download.1.pdf)

Configuration:
- Web browser and its version:90.0.4430.93
- Operating system and its version: mac 10.15.5
- PDF.js version: 2.9.146
- Is a browser extension:no

Steps to reproduce the problem:
1. The Chinese in the attachment cannot be rendered

Brower ✅
![image](https://user-images.githubusercontent.com/13477114/116678074-81782a00-a9db-11eb-8719-74f48fcebc2b.png)

PDF.js ❌ [https://mozilla.github.io/pdf.js/web/viewer.html](https://mozilla.github.io/pdf.js/web/viewer.html)
![image](https://user-images.githubusercontent.com/13477114/116678212-a371ac80-a9db-11eb-847f-dd1ad7752c13.png)


What is the expected behavior? (add screenshot)
**The Chinese character can be rendered**
What went wrong? (add screenshot)
**All of the Chinese character cannot be rendered**
Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension):

} else {
            glyphName = StandardEncoding[charCode];
          }
          if (!glyphName) {
            continue;
          }
          
          const standardGlyphName = recoverGlyphName(
            glyphName,
            glyphsUnicodeMap
          );
          let unicodeOrCharCode;
          if (cmapPlatformId === 3 && cmapEncodingId === 1) {
            unicodeOrCharCode = glyphsUnicodeMap[standardGlyphName];
          } else if (cmapPlatformId === 1 && cmapEncodingId === 0) {
            
            unicodeOrCharCode = MacRomanEncoding.indexOf(standardGlyphName);
          }
          for (let i = 0; i < cmapMappingsLength; ++i) {
            if (cmapMappings[i].charCode !== unicodeOrCharCode) {
              continue;
            }
            charCodeToGlyphId[charCode] = cmapMappings[i].glyphId;
            break;
          }
        }
      } else if (cmapPlatformId === 0) {
        
        for (let i = 0; i < cmapMappingsLength; ++i) {
          charCodeToGlyphId[cmapMappings[i].charCode] = cmapMappings[i].glyphId;