Switch to standard integer types in xxx/.

BUG=138542
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Review URL: https://codereview.chromium.org/1533283002

Cr-Commit-Position: refs/heads/master@{#366346}
diff --git a/sql/connection.h b/sql/connection.h
index 7a80077..e121b9fe 100644
--- a/sql/connection.h
+++ b/sql/connection.h
@@ -5,6 +5,7 @@
 #ifndef SQL_CONNECTION_H_
 #define SQL_CONNECTION_H_
 
+#include <stddef.h>
 #include <stdint.h>
 #include <map>
 #include <set>