Bug 1566315 - Add prefs to ignore_prefs r=njn

Adds prefs to `IGNORE_PREFS` so that they will be overlooked by lintpref. `devtools.console.stdout.chrome`, `devtools.console.stdout.content`, and `browser.dom.window.dump.enabled` make use of the `sticky` attribute, and `fission.autostart` makes use of the `locked` attribute within all.js.

Differential Revision: https://phabricator.services.mozilla.com/D44887

--HG--
extra : moz-landing-system : lando

tools/lint/libpref/__init__.py

@@ -15,8 +15,13 @@ from mozlint import result
 
 # If for any reason a pref needs to appear in both files, add it to this set.
 IGNORE_PREFS = {
+    'devtools.console.stdout.chrome',   # Uses the 'sticky' attribute.
+    'devtools.console.stdout.content',  # Uses the 'sticky' attribute.
+    'fission.autostart',                # Uses the 'locked' attribute.
+    'browser.dom.window.dump.enabled',  # Uses the 'sticky' attribute.
 }
 
+
 def get_names(pref_list_filename):
     pref_names = set()
     # We want to transform patterns like 'foo: @VAR@' into valid yaml. This