new prefs for talos

[jmaher]

Last week while investigating a crash on android which only happened in the reftest and talos harness (not in the mochitest harness), we compared the preferences. We found in mochitest we set a bunch of preferences to disable background network access (intentionally designed to 404 for mochitest):
// Point the url-classifier to the local testing server for fast failures
user_pref("browser.safebrowsing.gethashURL", "http://127.0.0.1:8888/safebrowsing-dummy/gethash");
user_pref("browser.safebrowsing.keyURL", "http://127.0.0.1:8888/safebrowsing-dummy/newkey");
user_pref("browser.safebrowsing.updateURL", "http://127.0.0.1:8888/safebrowsing-dummy/update");
// Point update checks to the local testing server for fast failures
user_pref("extensions.update.url", "http://127.0.0.1:8888/extensions-dummy/updateURL");
user_pref("extensions.update.background.url", "http://127.0.0.1:8888/extensions-dummy/updateBackgroundURL");
user_pref("extensions.blocklist.url", "http://127.0.0.1:8888/extensions-dummy/blocklistURL");
user_pref("extensions.hotfix.url", "http://127.0.0.1:8888/extensions-dummy/hotfixURL");
// Turn off extension updates so they don't bother tests
user_pref("extensions.update.enabled", false);
// Make sure opening about:addons won't hit the network
user_pref("extensions.webservice.discoverURL", "http://127.0.0.1:8888/extensions-dummy/discoveryURL");
// Make sure AddonRepository won't hit the network
user_pref("extensions.getAddons.maxResults", 0);
user_pref("extensions.getAddons.get.url", "http://127.0.0.1:8888/extensions-dummy/repositoryGetURL");
user_pref("extensions.getAddons.getWithPerformance.url", "http://127.0.0.1:8888/extensions-dummy/repositoryGetWithPerformanceURL");
user_pref("extensions.getAddons.search.browseURL", "http://127.0.0.1:8888/extensions-dummy/repositoryBrowseURL");
user_pref("extensions.getAddons.search.url", "http://127.0.0.1:8888/extensions-dummy/repositorySearchURL");
// Make sure that opening the plugins check page won't hit the network
user_pref("plugins.update.url", "http://127.0.0.1:8888/plugins-dummy/updateCheckURL");

We landed these prefs for android based reftests and the crash has gone away, we will be doing the same for talos. In thinking about it more, it makes sense to add these to desktop Talos as well.

Is there any reason why we shouldn't be setting these preferences for desktop Talos?

Should any of those be adjusted?

Thanks!