NTP: Avoid supervised user URL filter checks for non-SUs

These checks can be fairly expensive, and they're called on the critical
path for all navigations. No reason to pay the cost for non-SUs.

Bug: 786035
Change-Id: Id47d0b2fe4c86371fd4c277e363a4f7fcfd49194
Reviewed-on: https://chromium-review.googlesource.com/775959Reviewed-by: Charlie Harrison <csharrison@chromium.org>
Commit-Queue: Marc Treib <treib@chromium.org>
Cr-Commit-Position: refs/heads/master@{#517413}

chrome/browser/search/search.cc

@@ -95,6 +95,10 @@ bool IsNTPOrServiceWorkerURL(const GURL& url, Profile* profile) {
 
 bool IsURLAllowedForSupervisedUser(const GURL& url, Profile* profile) {
 #if BUILDFLAG(ENABLE_SUPERVISED_USERS)
+  // If this isn't a supervised user, skip the URL filter check, since it can be
+  // fairly expensive.
+  if (!profile->IsSupervised())
+    return true;
   SupervisedUserService* supervised_user_service =
       SupervisedUserServiceFactory::GetForProfile(profile);
   SupervisedUserURLFilter* url_filter = supervised_user_service->GetURLFilter();

chrome/browser/search/search_unittest.cc

@@ -350,6 +350,8 @@ TEST_F(SearchTest, UseLocalNTPIfNTPURLIsNotSet) {
 
 #if BUILDFLAG(ENABLE_SUPERVISED_USERS)
 TEST_F(SearchTest, UseLocalNTPIfNTPURLIsBlockedForSupervisedUser) {
+  // Mark the profile as supervised, otherwise the URL filter won't be checked.
+  profile()->SetSupervisedUserId("supervised");
   // Block access to foo.com in the URL filter.
   SupervisedUserService* supervised_user_service =
       SupervisedUserServiceFactory::GetForProfile(profile());