Attach (recommended) or Link to PDF file here:
https://drive.google.com/open?id=1UjLxnFw2g3gn3tvNLRYLdmG6mFdFKCcr

Configuration:
- Web browser and its version: Chrome 77.0.3865.90
- Operating system and its version: Mac mojave 10.14.6
- PDF.js version: 2.3.194
- Is a browser extension: Nope

Steps to reproduce the problem:
1. Make sure to set `renderInteractiveForms` to `true`
2. The read-only form field(Sample title) doesn't honor it's proper font-size

What is the expected behavior?
<img width="862" alt="write" src="https://user-images.githubusercontent.com/4616548/66152094-4a009a80-e64b-11e9-81dc-178068055efa.png">

What went wrong?
<img width="842" alt="wrong" src="https://user-images.githubusercontent.com/4616548/66152100-4d942180-e64b-11e9-91a8-ad9caf451f98.png">


let fontSize = this._defaultAppearanceData.fontSize;
    if (!fontSize) {
      const { fontColor, fontName } = this._defaultAppearanceData;
      let capHeight;
      if (font.capHeight) {
        capHeight = font.capHeight;
      } else {
        const glyphs = font.charsToGlyphs(font.encodeString("M").join(""));
        if (glyphs.length === 1 && glyphs[0].width) {
          const em = glyphs[0].width / 1000;
          
          
          capHeight = 0.7 * em;
        } else {
          capHeight = 0.7;
        }
      }
      
      fontSize = Math.max(1, Math.floor(height / (1.5 * capHeight)));
      this.data.defaultAppearance = createDefaultAppearance({
        fontSize,
        fontName,
        fontColor,
      });
    }
    return fontSize;
  }
  _renderText(text, font, fontSize, totalWidth, alignment, hPadding, vPadding) {