Bug 1638682 - Enable the 'Show in Firefox' option in the Unknown Content Type dialog. r=Gijs

Differential Revision: https://phabricator.services.mozilla.com/D75709

browser/app/profile/firefox.js

@@ -372,7 +372,7 @@ pref("browser.download.autohideButton", true);
 // This controls the visibility of the radio button in the
 // Unknown Content Type (Helper App) dialog that will open
 // the content in the browser.
-pref("browser.helperApps.showOpenOptionForPdfJS", false);
+pref("browser.helperApps.showOpenOptionForPdfJS", true);
 
 // search engines URL
 pref("browser.search.searchEnginesURL",      "https://addons.mozilla.org/%LOCALE%/firefox/search-engines/");