Zygote: create variables for magic fd numbers

content/browser/zygote_host_impl_linux.cc

 // 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.
 
 #include "content/browser/zygote_host_impl_linux.h"
 
 #include <sys/socket.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <unistd.h>
@@ skipping 85 matching lines @@
   int fds[2];
 #if defined(OS_FREEBSD) || defined(OS_OPENBSD)
   // The BSDs often don't support SOCK_SEQPACKET yet, so fall back to
   // SOCK_DGRAM if necessary.
   if (socketpair(PF_UNIX, SOCK_SEQPACKET, 0, fds) != 0)
     CHECK(socketpair(PF_UNIX, SOCK_DGRAM, 0, fds) == 0);
 #else
   CHECK(socketpair(PF_UNIX, SOCK_SEQPACKET, 0, fds) == 0);
 #endif
   base::FileHandleMappingVector fds_to_map;
-  fds_to_map.push_back(std::make_pair(fds[1], 3));
+  fds_to_map.push_back(std::make_pair(fds[1], content::kZygoteSocketPairFd));
 
   const CommandLine& browser_command_line = *CommandLine::ForCurrentProcess();
   if (browser_command_line.HasSwitch(switches::kZygoteCmdPrefix)) {
     cmd_line.PrependWrapper(
         browser_command_line.GetSwitchValueNative(switches::kZygoteCmdPrefix));
   }
   // Append any switches from the browser process that need to be forwarded on
   // to the zygote/renderers.
   // Should this list be obtained from browser_render_process_host.cc?
   static const char* kForwardSwitches[] = {
@@ skipping 37 matching lines @@
     }
   } else {
     LOG(WARNING) << "Running without the SUID sandbox! See "
         "http://code.google.com/p/chromium/wiki/LinuxSUIDSandboxDevelopment "
         "for more information on developing with the sandbox on.";
   }
 
   // Start up the sandbox host process and get the file descriptor for the
   // renderers to talk to it.
   const int sfd = RenderSandboxHostLinux::GetInstance()->GetRendererSocket();
-  fds_to_map.push_back(std::make_pair(sfd, 5));
+  fds_to_map.push_back(std::make_pair(sfd, content::kZygoteRendererSocketFd));
 
   int dummy_fd = -1;
   if (using_suid_sandbox_) {
     dummy_fd = socket(PF_UNIX, SOCK_DGRAM, 0);
     CHECK(dummy_fd >= 0);
-    fds_to_map.push_back(std::make_pair(dummy_fd, 7));
+    fds_to_map.push_back(std::make_pair(dummy_fd,
+                                        content::kZygoteIdFd));
   }
 
   base::ProcessHandle process = -1;
   base::LaunchOptions options;
   options.fds_to_remap = &fds_to_map;
   base::LaunchProcess(cmd_line.argv(), options, &process);
   CHECK(process != -1) << "Failed to launch zygote process";
 
   if (using_suid_sandbox_) {
     // In the SUID sandbox, the real zygote is forked from the sandbox.
@@ skipping 309 matching lines @@
 
 pid_t ZygoteHostImpl::GetSandboxHelperPid() const {
   return RenderSandboxHostLinux::GetInstance()->pid();
 }
 
 int ZygoteHostImpl::GetSandboxStatus() const {
   if (have_read_sandbox_status_word_)
     return sandbox_status_;
   return 0;
 }