Fix memtrack_helper for newer versions Android.

tools/android/memtrack_helper/memtrack_helper_test_client.c

 /*
  * Copyright 2015 The Chromium Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/socket.h>
@@ skipping 17 matching lines @@
   struct sockaddr_un server_addr;
   init_memtrack_server_addr(&server_addr);
 
   if (connect(sock, (struct sockaddr*)&server_addr, sizeof(server_addr)))
     exit_with_failure("connect");
 
   if (send(sock, pid, strlen(pid) + 1, 0) < 0)
     exit_with_failure("send");
 
   char buf[4096];
-  memset(buf, 0, sizeof(buf));
-  if (recv(sock, buf, sizeof(buf), 0) <= 0)
+  ssize_t rsize = recv(sock, buf, sizeof(buf) - 1, 0);
+  if (rsize < 0)
     exit_with_failure("recv");
+  buf[rsize] = '\0';
 
   puts(buf);
   return EXIT_SUCCESS;
 }