Define magic descriptors in one place.

content/common/zygote_commands_linux.h

Index: content/common/zygote_commands_linux.h
diff --git a/content/common/zygote_commands_linux.h b/content/common/zygote_commands_linux.h
index 6df1fdae2876b0fca9ab13f6d9be78bb230d9466..717173cdf5634b026846879ffc6cdd4d74fe3d3f 100644
--- a/content/common/zygote_commands_linux.h
+++ b/content/common/zygote_commands_linux.h
@@ -5,6 +5,8 @@
 #ifndef CONTENT_COMMON_ZYGOTE_COMMANDS_LINUX_H_
 #define CONTENT_COMMON_ZYGOTE_COMMANDS_LINUX_H_
 
+#include "content/common/child_process_sandbox_support_impl_linux.h"
+
 namespace content {
 
 // Contents of the initial message sent from the zygote to the browser when it
@@ -15,8 +17,9 @@ static const char kZygoteHelloMessage[] = "ZYGOTE_OK";
 const size_t kZygoteMaxMessageLength = 8192;
 
 // File descriptors initialized by the Zygote Host
-const int kZygoteSocketPairFd = 3;
-const int kZygoteRendererSocketFd = 5;
+const int kMagicZygoteDescriptor =

[agl, 2013/09/09 16:59:07]

This renaming seems superfluous.

+    kPrimaryIPCChannel + base::GlobalDescriptors::kBaseDescriptor;
+const int kMagicSandboxIPCDescriptor = GetSandboxFD();

[agl, 2013/09/09 16:59:07]

No global initialisers.

 // This file descriptor is special. It is passed to the Zygote and a setuid
 // helper will be called to locate the process of the Zygote on the system.
 // This mechanism is used when multiple PID namespaces exist because of the