Add translations of "Allow access to file URLs"

The JSON file is generated as follows.

1. Go to the src/chrome/app/resources directory of Chromium's source.

2. Find the translation ID of the "Allow access to file URLs" string:

grep 'Allow access to file URLs' generated_resources_en-GB.xtb

3. With the ID that you've found, locate the other translations.

grep 3341703758641437857 generated_resources_*.xtb

4. If the result looks OK, serialize the result as JSON and save it.

> path/to/pdf.js/web/chrome-i18n-allow-access-to-file-urls.json \
python -c "import json;print(json.dumps({ \
$(grep 3341703758641437857 generated_resources_*.xtb | \
 sed "s@generated_resources_\([^.]\+\)\.xtb:<translation[^>]\+>\(.\+\)</translation>@'\1':'''\2''',@" \
)}, sort_keys=True, indent=2))"

(Strings are taken from Chromium 45.0.2448.0 (ccrev.com/337313).

web/viewer-snippet-chrome-overlays.html

@@ -14,7 +14,9 @@
           font-size: 14px;
           line-height: 1.8em;
           word-break: break-all;">
-        Click on "Allow access to file URLs" at
+        Click on
+        "<span id="chrome-file-access-label">Allow access to file URLs</span>"
+        at
         <a id="chrome-link-to-extensions-page">chrome://extensions</a>
         <br>
         to view <span id="chrome-url-of-local-file">this PDF file.</span>