Expand comment for named IPC chmod().

ipc/ipc_channel_posix.cc

Index: ipc/ipc_channel_posix.cc
diff --git a/ipc/ipc_channel_posix.cc b/ipc/ipc_channel_posix.cc
index 07d205a9b969d651f2c47a116b3cdb4ee5a02e62..0d48d47495764c6fb69d61008233290e685fafb1 100644
--- a/ipc/ipc_channel_posix.cc
+++ b/ipc/ipc_channel_posix.cc
@@ -193,9 +193,13 @@ bool CreateServerUnixDomainSocket(const std::string& pipe_name,
     return false;
   }
 
-  // Adjust the socket permissions.
+  // Adjust the socket permissions as a precaution on ChromeOS.

[Wez, 2011/02/25 10:23:14]

Nit: We're adjusting the permissions even on Linux & Mac, not just on ChromeOS. 
Could say "Explicitly set file system permissions on socket, mainly as a
precaution for ChromeOS"?

+  // Do not rely on these file permissions to provide security - the file is
+  // created during the above bind() call so there is still a window for
+  // malicious abuse because the file exists between bind() and chmod(). Also,
+  // the file permissions may not be enforced for unix sockets on all platforms.
   if (chmod(pipe_name.c_str(), 0600)) {
-    PLOG(ERROR) << "fchmod " << pipe_name;
+    PLOG(ERROR) << "chmod " << pipe_name;
     if (HANDLE_EINTR(close(fd)) < 0)
       PLOG(ERROR) << "close " << pipe_name;
     return false;