NaCl: Clean up how FDs are passed to nacl_helper instances on Linux

content/public/common/zygote_fork_delegate_linux.h

Index: content/public/common/zygote_fork_delegate_linux.h
diff --git a/content/public/common/zygote_fork_delegate_linux.h b/content/public/common/zygote_fork_delegate_linux.h
index a5ea9f2952f6eebeea745f1ec39496cc2799ee5b..c900a843beac5e368502cc8a084b4b635d4b74df 100644
--- a/content/public/common/zygote_fork_delegate_linux.h
+++ b/content/public/common/zygote_fork_delegate_linux.h
@@ -43,6 +43,17 @@ class ZygoteForkDelegate {
   virtual bool CanHelp(const std::string& process_type, std::string* uma_name,
                        int* uma_sample, int* uma_boundary_value) = 0;
 
+  // Indexes of FDs in the vector passed to Fork().
+  enum {
+    // Used to pass in the descriptor for talking to the Browser
+    kBrowserFDIndex = 0,
+    // The next two are used in the protocol for discovering the
+    // child processes real PID from within the SUID sandbox. See
+    // http://code.google.com/p/chromium/wiki/LinuxZygote
+    kDummyFDIndex = 1,
+    kParentFDIndex = 2

[jln (very slow on Chromium), 2013/10/07 18:12:06]

With MACRO_STYLE, in Chromium, it's typical to have a *_END member at the end to
be used as a count. In this case it could be kNumPassedFds or something similar.

(Also FYI, strictly speaking the Chromium style guide says to continue using
MACRO_STYLE for enums. In this case the enum is merely a way to define constants
and never used as a type, so I think your way is better).

[Mark Seaborn, 2013/10/08 18:31:06]

Added kNumPassedFds.
OK, I've left it as the "k*" style.

+  };
+
   // Delegate forks, returning a -1 on failure. Outside the
   // suid sandbox, Fork() returns the Linux process ID.
   // This method is not aware of any potential pid namespaces, so it'll