Link to PDF file (or attach file here): [detect-form-fields.pdf](https://github.com/mozilla/pdf.js/files/287227/detect-form-fields.pdf)

Configuration:
- Web browser and its version: Firefox 46.0.1
- Operating system and its version: Ubuntu 16.04
- PDF.js version: 1.3.231
- Is an extension: No

Steps to reproduce the problem:
1. Open PDF
2. Look at entered text in form sections 8a and 9a

What is the expected behavior? Text is correct size:

![screenshot from 2016-05-27 12-32-04](https://cloud.githubusercontent.com/assets/33672/15619145/32ff065a-2407-11e6-8cfb-95905526fd91.png)

What went wrong? Text is very large:

![screenshot from 2016-05-27 12-30-58](https://cloud.githubusercontent.com/assets/33672/15619160/45016442-2407-11e6-85c0-faee9879c20d.png)

PdfBug console output:

```
11:56:13.291 PDF ef2293a3b9f4e0accbef97ee38798a2c [1.3 Mac OS X 10.11.1 Quartz PDFContext / Amgraf OneForm Designer Plus] (PDF.js: 1.3.231)1 viewer.js:6800:7
11:56:13.292 Warning: AcroForm/XFA is not supported1 viewer.js:6824:9
11:56:13.424 Warning: Unimplemented annotation type "FreeText", falling back to base annotation1 pdf.worker.js:9407:5
11:56:13.806 Warning: fontRes not available1 pdf.worker.js:9407:5 (logged 54 times)
11:56:13.898 Warning: Error during font loading: Font Helvetica-Bold is not available1 pdf.js:368:5
```

const BACKGROUND_ENLIGHT = 0.7;
    const wrapper = document.createElement("div");
    wrapper.className = "popupWrapper";
    
    
    
    
    this.hideElement = this.hideWrapper ? wrapper : this.container;
    this.hideElement.setAttribute("hidden", true);
    const popup = document.createElement("div");
    popup.className = "popup";
    const color = this.color;
    if (color) {
      
      const r = BACKGROUND_ENLIGHT * (255 - color[0]) + color[0];
      const g = BACKGROUND_ENLIGHT * (255 - color[1]) + color[1];
      const b = BACKGROUND_ENLIGHT * (255 - color[2]) + color[2];
      popup.style.backgroundColor = Util.makeHexColor(r | 0, g | 0, b | 0);
    }
    const title = document.createElement("h1");
    title.textContent = this.title;
    popup.appendChild(title);
    
    
    
    const dateObject = PDFDateString.toDateObject(this.modificationDate);
    if (dateObject) {
      const modificationDate = document.createElement("span");
      modificationDate.textContent = "{{date}}, {{time}}";
      modificationDate.dataset.l10nId = "annotation_date_string";