IWYU: add stdint.h for int types in base/containers

Bug: chromium:957519
Change-Id: Iea60680ebf9b61a101567d096154e2d9263f1581
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/15240
Reviewed-by: Takuto Ikuta <tikuta@google.com>
Commit-Queue: Takuto Ikuta <tikuta@google.com>

src/base/containers/span.h

diff --git a/src/base/containers/span.h b/src/base/containers/span.h
index 4af83b4..19b9503 100644
--- a/src/base/containers/span.h
+++ b/src/base/containers/span.h
@@ -6,6 +6,7 @@
 #define BASE_CONTAINERS_SPAN_H_
 
 #include <stddef.h>
+#include <stdint.h>
 
 #include <algorithm>
 #include <array>