Bug 1524873 - Enable SafeBrowsing in Safe Mode. r=gcp

This patch enables SafeBrowsing in Safe Mode because features based
on SafeBrowsing are essential for Firefox(For example, Enhanced Tracking Protection).

Since Safe Browsing update is nondeterministic, we disable periodical
SafeBrowsing update to make troubleshooting easier. Manually trigger an
update via about:classifier is still enabled.

Last, SafeBrowsing tables provided by Google will be ignored in Safe
Mode to ensure the SafeBrowsing warnings are update-to-date.

Differential Revision: https://phabricator.services.mozilla.com/D62708

toolkit/components/url-classifier/Classifier.cpp

@@ -1564,6 +1564,17 @@ RefPtr<LookupCache> Classifier::GetLookupCache(const nsACString& aTable,
   //        '-proto'.
   RefPtr<LookupCache> cache;
   nsCString provider = GetProvider(aTable);
+
+  // Google requests SafeBrowsing related feature should only be enabled when
+  // the databases are update-to-date. Since we disable Safe Browsing update in
+  // Safe Mode, ignore tables provided by Google to ensure we don't show
+  // outdated warnings.
+  if (nsUrlClassifierUtils::IsInSafeMode()) {
+    if (provider.EqualsASCII("google") || provider.EqualsASCII("google4")) {
+      return nullptr;
+    }
+  }
+
   if (StringEndsWith(aTable, NS_LITERAL_CSTRING("-proto"))) {
     cache = new LookupCacheV4(aTable, provider, rootStoreDirectory);
   } else {