Use constexpr TaskTraits constructor in components.

components/nacl/browser/nacl_browser.cc

Index: components/nacl/browser/nacl_browser.cc
diff --git a/components/nacl/browser/nacl_browser.cc b/components/nacl/browser/nacl_browser.cc
index 1d9f29dd495dadaa603b65d487bf922c71c7a792..7d258128a7992fa585394271272c5923143e22f5 100644
--- a/components/nacl/browser/nacl_browser.cc
+++ b/components/nacl/browser/nacl_browser.cc
@@ -377,9 +377,7 @@ void NaClBrowser::EnsureValidationCacheAvailable() {
       // task and further file access will not occur until after we get a
       // response.
       base::PostTaskWithTraitsAndReply(
-          FROM_HERE,
-          base::TaskTraits().MayBlock().WithPriority(
-              base::TaskPriority::BACKGROUND),
+          FROM_HERE, {base::MayBlock(), base::TaskPriority::BACKGROUND},
           base::Bind(ReadCache, validation_cache_file_path_, data),
           base::Bind(&NaClBrowser::OnValidationCacheLoaded,
                      base::Unretained(this), base::Owned(data)));