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

sandbox/linux/suid/common/sandbox.h

 // 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.
 
 #ifndef SANDBOX_LINUX_SUID_SANDBOX_H_
 #define SANDBOX_LINUX_SUID_SANDBOX_H_
 
 #if defined(__cplusplus)
 namespace sandbox {
 #endif
 
 // These are command line switches that may be used by other programs
 // (e.g. Chrome) to construct a command line for the sandbox.
 static const char kAdjustOOMScoreSwitch[] = "--adjust-oom-score";
-#if defined(OS_CHROMEOS)
-static const char kAdjustLowMemMarginSwitch[] = "--adjust-low-mem";
-#endif
 
 static const char kSandboxDescriptorEnvironmentVarName[] = "SBX_D";
 static const char kSandboxHelperPidEnvironmentVarName[] = "SBX_HELPER_PID";
 
 static const long kSUIDSandboxApiNumber = 1;
 static const char kSandboxEnvironmentApiRequest[] = "SBX_CHROME_API_RQ";
 static const char kSandboxEnvironmentApiProvides[] = "SBX_CHROME_API_PRV";
 
 // This number must be kept in sync with common/zygote_commands_linux.h
 static const int kZygoteIdFd = 7;
 
 // These are the magic byte values which the sandboxed process uses to request
 // that it be chrooted.
 static const char kMsgChrootMe = 'C';
 static const char kMsgChrootSuccessful = 'O';
 
 // These are set if we have respectively switched to a new PID or NET namespace
 // by going through the setuid binary helper.
 static const char kSandboxPIDNSEnvironmentVarName[] = "SBX_PID_NS";
 static const char kSandboxNETNSEnvironmentVarName[] = "SBX_NET_NS";
 
 #if defined(__cplusplus)
 }  // namespace sandbox
 #endif
 
 #endif  // SANDBOX_LINUX_SUID_SANDBOX_H_