Add include for CHAR_BIT

Fix build error about undefined CHAR_BIT.

Change-Id: I72824f009742bc3d7dcb04e6e83a3c8790169df9
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/233114
Commit-Queue: David Neto <dneto@google.com>
Reviewed-by: Brandon Jones <bajones@chromium.org>
Auto-Submit: dan sinclair <dsinclair@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
diff --git a/src/dawn/common/Math.h b/src/dawn/common/Math.h
index 1466345..0fc6788 100644
--- a/src/dawn/common/Math.h
+++ b/src/dawn/common/Math.h
@@ -28,6 +28,7 @@
 #ifndef SRC_DAWN_COMMON_MATH_H_
 #define SRC_DAWN_COMMON_MATH_H_
 
+#include <climits>
 #include <cstddef>
 #include <cstdint>
 #include <cstring>