Use constexpr TaskTraits constructor in chrome.

chrome/browser/captive_portal/captive_portal_browsertest.cc

Index: chrome/browser/captive_portal/captive_portal_browsertest.cc
diff --git a/chrome/browser/captive_portal/captive_portal_browsertest.cc b/chrome/browser/captive_portal/captive_portal_browsertest.cc
index 75bdd53ef4e15f255984d8d84ca59d0d89d9e3bd..d3b5668cde5146cf2e6e4e71f34653bd9bbe34f7 100644
--- a/chrome/browser/captive_portal/captive_portal_browsertest.cc
+++ b/chrome/browser/captive_portal/captive_portal_browsertest.cc
@@ -482,7 +482,7 @@ URLRequestMockCaptivePortalJobFactory::Interceptor::MaybeInterceptRequest(
     net::NetworkDelegate* network_delegate) const {
   EXPECT_TRUE(BrowserThread::CurrentlyOn(BrowserThread::IO));
 
-  const base::TaskTraits kTraits = base::TaskTraits().MayBlock();
+  const base::TaskTraits kTraits = {base::MayBlock()};
 
   // The PathService is threadsafe.
   base::FilePath root_http;