IWYU: add stdint.h for int types in tint::utils

Bug: chromium:957519
Change-Id: I867cdff638388c3f2a35f58b67763413a4e50df2
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/128520
Auto-Submit: Stephan Hartmann <stha09@googlemail.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
diff --git a/src/tint/utils/math.h b/src/tint/utils/math.h
index c10a2c9..311ec16 100644
--- a/src/tint/utils/math.h
+++ b/src/tint/utils/math.h
@@ -15,6 +15,8 @@
 #ifndef SRC_TINT_UTILS_MATH_H_
 #define SRC_TINT_UTILS_MATH_H_
 
+#include <stdint.h>
+
 #include <string>
 #include <type_traits>