Simplify ZygoteForkDelegate API further

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 0e926ea009382b692d0fde0340c50e2bf467b0cf..58028ca0e8129f342d0fa00f8d640bb8e24c16cc 100644
--- a/content/public/common/zygote_fork_delegate_linux.h
+++ b/content/public/common/zygote_fork_delegate_linux.h
@@ -59,13 +59,11 @@ class ZygoteForkDelegate {
   // suid sandbox, Fork() returns the Linux process ID.
   // This method is not aware of any potential pid namespaces, so it'll
   // return a raw pid just like fork() would.
+  // Delegate is responsible for communicating the channel ID to the
+  // newly created child process.
   virtual pid_t Fork(const std::string& process_type,
-                     const std::vector<int>& fds) = 0;
-
-  // After a successful fork, signal the child to indicate that
-  // the child's PID has been received. Also communicate the
-  // channel ID as a part of acknowledgement message.
-  virtual bool AckChild(int fd, const std::string& channel_id) = 0;
+                     const std::vector<int>& fds,
+                     const std::string& channel_id) = 0;
 
   // The fork delegate must also assume the role of waiting for its children
   // since the caller will not be their parents and cannot do it. |pid| here