Test case to exercise the different encodings:
1. Create a file "some file#@%M<br>%25 .pdf"
2. Build the extension with `gulp chromium` and load it in Chrome.
3. Go to `chrome://extensions/` and ensure that the
"Allow access to file URLs" is disabled.
4. Try to open the file from step 1 in Chrome (maybe reload once).
5. PDF.js should be showing a file chooser button.
6. Click on that button and select a different file.
Test: Check that a confirmation dialog pops up that warns about
a different file name. Cancel the dialog.
7. Click on the button again and select the original file.
Test: Check that the file opens as expected.
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