Some C++11 cleanup of history types.

components/query_parser/snippet.h

Index: components/query_parser/snippet.h
diff --git a/components/query_parser/snippet.h b/components/query_parser/snippet.h
index ed6a887cb8f453cdb97ac586a60eaddc2ee6728e..11f05d6bcdccb32b39b2821a33ddf134aa3ead41 100644
--- a/components/query_parser/snippet.h
+++ b/components/query_parser/snippet.h
@@ -48,8 +48,11 @@ class Snippet {
 
   Snippet();
   Snippet(const Snippet& other);
+  Snippet(Snippet&& other) noexcept;
   ~Snippet();
 
+  Snippet& operator=(const Snippet&);
+
   // Given |matches|, the match positions within |document|, compute the snippet
   // for the document.
   // Note that |document| is UTF-8 and the offsets in |matches| are byte