cros: Remove unused low memory margin code from sandbox and zygote

sandbox/linux/suid/sandbox.c

 // Copyright (c) 2012 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.
 
 // http://code.google.com/p/chromium/wiki/LinuxSUIDSandbox
 
 #include "common/sandbox.h"
 
 #define _GNU_SOURCE
 #include <asm/unistd.h>
@@ skipping 432 matching lines @@
       return 1;
     pid_t pid = pid_ul;
     endptr = NULL;
     errno = 0;
     score = strtol(argv[3], &endptr, 10);
     if (score == LONG_MAX || score == LONG_MIN ||
         !endptr || *endptr || errno != 0)
       return 1;
     return AdjustOOMScore(pid, score);
   }
-#if defined(OS_CHROMEOS)
-  if (argc == 3 && (0 == strcmp(argv[1], kAdjustLowMemMarginSwitch))) {
-    char* endptr = NULL;
-    errno = 0;
-    unsigned long margin_mb = strtoul(argv[2], &endptr, 10);
-    if (!endptr || *endptr || errno != 0)
-      return 1;
-    return AdjustLowMemoryMargin(margin_mb);
-  }
-#endif
 
   // Protect the core setuid sandbox functionality with an API version
   if (!CheckAndExportApiVersion()) {
     return 1;
   }
 
   if (!MoveToNewNamespaces())
     return 1;
   if (!SpawnChrootHelper())
     return 1;
   if (!DropRoot())
     return 1;
   if (!SetupChildEnvironment())
     return 1;
 
   execv(argv[1], &argv[1]);
   FatalError("execv failed");
 
   return 1;
 }