Switch to standard integer types in components/, part 3 of 4.

components/proximity_auth/fake_secure_context.cc

Index: components/proximity_auth/fake_secure_context.cc
diff --git a/components/proximity_auth/fake_secure_context.cc b/components/proximity_auth/fake_secure_context.cc
index f5d20d70eb934816eebbae8ff22da0f2de72b3d0..92e54b05d284fb822a7fad2d48869ccbca5b687d 100644
--- a/components/proximity_auth/fake_secure_context.cc
+++ b/components/proximity_auth/fake_secure_context.cc
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include <stddef.h>
+
 #include "components/proximity_auth/fake_secure_context.h"
 
 namespace proximity_auth {