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

sandbox/linux/suid/sandbox.c

Index: sandbox/linux/suid/sandbox.c
diff --git a/sandbox/linux/suid/sandbox.c b/sandbox/linux/suid/sandbox.c
index 32435a7ad89f2a6440f855ebbd56b4824c92cc7e..a161e1932da84bfdc0dc145c2b2ab665bef1be91 100644
--- a/sandbox/linux/suid/sandbox.c
+++ b/sandbox/linux/suid/sandbox.c
@@ -450,16 +450,6 @@ int main(int argc, char **argv) {
       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()) {