Linux: refactor zygote support

http://code.google.com/p/chromium/wiki/LinuxZygote

  * Move Chrome specific bits out of base
  * Move away from the idea of reserved file descriptors (which don't really work
  with zygotes)
  * Load resources before forking renderers (means that we don't need
  communication between the zygote process and the renderers)
  * Make sure that gdb works against the browser again
  * Make sure that we have different ASLR between the renderers and the browser.

http://codereview.chromium.org/119335

(This is a reland. First landed in r18109, reverted in r18112.)


git-svn-id: svn://svn.chromium.org/chrome/trunk/src@18291 0039d316-1c4b-4281-b951-d872f2087c98

diff --git a/chrome/common/ipc_channel.h b/chrome/common/ipc_channel.h
index f619508..85b35fa 100644
--- a/chrome/common/ipc_channel.h
+++ b/chrome/common/ipc_channel.h

@@ -87,14 +87,13 @@
 
 #if defined(OS_POSIX)
   // On POSIX an IPC::Channel wraps a socketpair(), this method returns the
-  // FD # for the client end of the socket and the equivalent FD# to use for
-  // mapping it into the Child process.
+  // FD # for the client end of the socket.
   // This method may only be called on the server side of a channel.
   //
   // If the kTestingChannelID flag is specified on the command line then
   // a named FIFO is used as the channel transport mechanism rather than a
-  // socketpair() in which case this method returns -1 for both parameters.
-  void GetClientFileDescriptorMapping(int *src_fd, int *dest_fd) const;
+  // socketpair() in which case this method returns -1.
+  int GetClientFileDescriptor() const;
 #endif  // defined(OS_POSIX)
 
  private: