check(pref_service->GetDefaultBranch("browser.display",
getter_AddRefs(pref_branch)));
check(pref_branch->SetIntPref("screen_resolution", 40));
check(pref_service->GetDefaultBranch("browser.display",
getter_AddRefs(pref_branch)));
check(pref_branch->SetIntPref("screen_resolution", 40));