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
```

}
    }
    
    for (const option of this.data.options) {
      const optionElement = document.createElement("option");
      optionElement.textContent = option.displayValue;
      optionElement.value = option.exportValue;
      if (this.data.fieldValue.includes(option.exportValue)) {
        optionElement.setAttribute("selected", true);
      }
      selectElement.appendChild(optionElement);
    }
    function getValue(event) {
      const options = event.target.options;
      return options[options.selectedIndex].value;
    }
    if (this.enableScripting && this.hasJSActions) {
      selectElement.addEventListener("updatefromsandbox", event => {
        const { detail } = event;
        const actions = {
          value() {
            const options = event.target.options;
            const value = detail.value;
            const i = options.indexOf(value);
            if (i !== -1) {
              options.selectedIndex = i;
              storage.setValue(id, { value });
            }
          },
          focus() {