Switch to standard integer types in base/.

BUG=138542
[email protected]
NOPRESUBMIT=true

Review URL: https://codereview.chromium.org/1538743002

Cr-Commit-Position: refs/heads/master@{#366910}
diff --git a/base/pickle.h b/base/pickle.h
index 8e82c62..02bc432 100644
--- a/base/pickle.h
+++ b/base/pickle.h
@@ -5,6 +5,7 @@
 #ifndef BASE_PICKLE_H_
 #define BASE_PICKLE_H_
 
+#include <stddef.h>
 #include <stdint.h>
 
 #include <string>