Make NTPTile copyable.

components/ntp_tiles/ntp_tile.cc

Index: components/ntp_tiles/ntp_tile.cc
diff --git a/components/ntp_tiles/ntp_tile.cc b/components/ntp_tiles/ntp_tile.cc
index 82d16ce450f808b380c5f4f90ecb522e55bdc149..ece28625aa40c6791cc4b5242af7c0b7e02c4588 100644
--- a/components/ntp_tiles/ntp_tile.cc
+++ b/components/ntp_tiles/ntp_tile.cc
@@ -8,10 +8,8 @@ namespace ntp_tiles {
 
 NTPTile::NTPTile() : source(NTPTileSource::TOP_SITES) {}
 
+NTPTile::NTPTile(const NTPTile&) = default;
+
 NTPTile::~NTPTile() {}
 
-NTPTile::NTPTile(NTPTile&&) = default;
-
-NTPTile& NTPTile::operator=(NTPTile&&) = default;
-
 }  // namespace ntp_tiles