Attach (recommended) or Link to PDF file here:
https://www.nta.go.jp/taxes/tetsuzuki/shinsei/annai/joyaku/annai/pdf2/250.pdf

Configuration:
- Web browser and its version: Firefox 81.0a1
- Operating system and its version: Debian 5.6.7-1
- PDF.js version: latest in Firefox nightly
- Is a browser extension: No

Steps to reproduce the problem:
1. Open the pdf and paste the following text "本 店 又 は 主 た る 事 務 所 の 所 在 地" in "Full name" and in "Domicile and residence" textfields
2. Print or Save the pdf 

What is the expected behavior? (add screenshot)
![image](https://user-images.githubusercontent.com/5641725/91207547-30f05480-e709-11ea-9abd-2af5d970dc46.png)

What went wrong? (add screenshot)
![image](https://user-images.githubusercontent.com/5641725/91207663-69902e00-e709-11ea-8a1d-1ddd30cf0621.png)

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

glyphId,
            });
          }
        } else {
          warn("cmap table has unsupported format: " + format);
          return {
            platformId: -1,
            encodingId: -1,
            mappings: [],
            hasShortCmap: false,
          };
        }
        
        mappings.sort(function (a, b) {
          return a.charCode - b.charCode;
        });
        for (i = 1; i < mappings.length; i++) {
          if (mappings[i - 1].charCode === mappings[i].charCode) {
            mappings.splice(i, 1);
            i--;
          }
        }
        return {
          platformId: potentialTable.platformId,
          encodingId: potentialTable.encodingId,
          mappings,
          hasShortCmap,
        };
      }
      function sanitizeMetrics(