This patch is the first step towards implementing support for
interactive forms (AcroForms). It makes it possible to render text
widget annotations exactly like Adobe Reader/Acrobat.
Everything we implement for AcroForms is disabled by default using a
preference, mainly because it is not ready to use yet, but has to
implemented in many steps to avoid complexity. The preference allows us
to work with the code while not exposing the behavior by default. Mainly
storing entered values and printing them is still absent, which would be
minimal requirements for enabling this by default.
Privacy policy: https://github.com/Rob--W/pdfjs-telemetry#privacy-policy
Unit tests (offline):
```
node test/chromium/test-telemetry.js
```
Server tests (requires that Nginx is installed):
```
git clone https://github.com/Rob--W/pdfjs-telemetry.git
cd pdfjs-telemetry/
python testserver.py TestHttp TestHttps
```
Integration test (extension + server):
- Build the extension
- Edit build/chromium/telemetry.js and remove the check for
chrome.runtime.id.
- Start Chrome (preferably a new profile):
chromium --user-data-dir=/tmp/pdftest --no-first-run
- Open chrome://net-internals#events
- Visit chrome://extensions and enable Developer mode.
- Load unpacked extension, select build/chromium.
- Go to the chrome://net-internals tab and filter on pdfjs.robwu.nl.
- Click on URL_REQUEST and verify that the server replied with 204.
- Reload the extension.
- Verify that chrome://net-internals did not contain a new log request.
