perfetto: add include for size_t

Change-Id: I33faf83d014c99f671c78d43ffdc4dbc5d40bdd8
diff --git a/src/android_internal/statsd.h b/src/android_internal/statsd.h
index 8afa9f0..f114aa2 100644
--- a/src/android_internal/statsd.h
+++ b/src/android_internal/statsd.h
@@ -17,6 +17,7 @@
 #ifndef SRC_ANDROID_INTERNAL_STATSD_H_
 #define SRC_ANDROID_INTERNAL_STATSD_H_
 
+#include <stddef.h>
 #include <stdint.h>
 
 // This header declares proxy functions defined in