Move ntp_tiles classes to namespace ntp_tiles.

components/ntp_tiles/most_visited_sites_unittest.cc

Index: components/ntp_tiles/most_visited_sites_unittest.cc
diff --git a/components/ntp_tiles/most_visited_sites_unittest.cc b/components/ntp_tiles/most_visited_sites_unittest.cc
index 36bfcb7cb7b4af62e3668f4461bc605942583cfc..151a2c2dbfab7175f83d224b24a8379e8ef1cdd6 100644
--- a/components/ntp_tiles/most_visited_sites_unittest.cc
+++ b/components/ntp_tiles/most_visited_sites_unittest.cc
@@ -14,6 +14,8 @@
 #include "base/strings/utf_string_conversions.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+namespace ntp_tiles {
+
 namespace {
 
 struct TitleURL {
@@ -137,3 +139,5 @@ TEST_F(MostVisitedSitesTest, PersonalPrecedePopularSites) {
   Check(popular_sites, std::vector<TitleURL>(), personal_sites,
         expected_sites_source, expected_sites);
 }
+
+}  // namespace ntp_tiles