Define magic descriptors in one place.

content/browser/zygote_host/zygote_host_impl_linux.cc

Index: content/browser/zygote_host/zygote_host_impl_linux.cc
diff --git a/content/browser/zygote_host/zygote_host_impl_linux.cc b/content/browser/zygote_host/zygote_host_impl_linux.cc
index bb84e62ce3aaee5e072c9c1ad94bd7ef65e130ed..3490ff312457f067ab3803ae566ebf9fe44c44bf 100644
--- a/content/browser/zygote_host/zygote_host_impl_linux.cc
+++ b/content/browser/zygote_host/zygote_host_impl_linux.cc
@@ -86,7 +86,7 @@ void ZygoteHostImpl::Init(const std::string& sandbox_cmd) {
   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], kZygoteSocketPairFd));
+  fds_to_map.push_back(std::make_pair(fds[1], kMagicZygoteDescriptor));
 
   const CommandLine& browser_command_line = *CommandLine::ForCurrentProcess();
   if (browser_command_line.HasSwitch(switches::kZygoteCmdPrefix)) {
@@ -149,7 +149,7 @@ void ZygoteHostImpl::Init(const std::string& sandbox_cmd) {
   // 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, kZygoteRendererSocketFd));
+  fds_to_map.push_back(std::make_pair(sfd, kMagicSandboxIPCDescriptor));
 
   int dummy_fd = -1;
   if (using_suid_sandbox_) {