Simplify ZygoteForkDelegate API further

content/zygote/zygote_linux.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/zygote/zygote_linux.h"
 
 #include <fcntl.h>
 #include <string.h>
 #include <sys/socket.h>
 #include <sys/types.h>
@@ skipping 315 matching lines @@
   if (use_helper) {
     std::vector<int> fds;
     int ipc_channel_fd = LookUpFd(fd_mapping, kPrimaryIPCChannel);
     if (ipc_channel_fd < 0) {
       DLOG(ERROR) << "Failed to find kPrimaryIPCChannel in FD mapping";
       goto error;
     }
     fds.push_back(ipc_channel_fd);  // kBrowserFDIndex
     fds.push_back(dummy_fd);  // kDummyFDIndex
     fds.push_back(pipe_fds[0]);  // kParentFDIndex
-    pid = helper_->Fork(process_type, fds);
+    pid = helper_->Fork(process_type, fds, channel_id);
   } else {
     pid = fork();
   }
   if (pid < 0) {
     goto error;
   } else if (pid == 0) {
     // In the child process.
     close(pipe_fds[1]);
     base::ProcessId real_pid;
     // Wait until the parent process has discovered our PID.  We
@@ skipping 56 matching lines @@
     }
 
     // Now set-up this process to be tracked by the Zygote.
     if (process_info_map_.find(real_pid) != process_info_map_.end()) {
       LOG(ERROR) << "Already tracking PID " << real_pid;
       NOTREACHED();
     }
     process_info_map_[real_pid].internal_pid = pid;
     process_info_map_[real_pid].started_from_helper = use_helper;
 
-    if (use_helper) {
-      if (!helper_->AckChild(pipe_fds[1], channel_id)) {
-        LOG(ERROR) << "Failed to synchronise with zygote fork helper";
-        goto error;
-      }
-    } else {
-      int written =
-          HANDLE_EINTR(write(pipe_fds[1], &real_pid, sizeof(real_pid)));
-      if (written != sizeof(real_pid)) {
-        LOG(ERROR) << "Failed to synchronise with child process";
-        goto error;
-      }
+    // If we're using a helper, we still need to let the child process know
+    // we've discovered its real PID, but we don't actually reveal the PID.
+    const base::ProcessId pid_for_child = use_helper ? 0 : real_pid;
+    ssize_t written =
+        HANDLE_EINTR(write(pipe_fds[1], &pid_for_child, sizeof(pid_for_child)));
+    if (written != sizeof(pid_for_child)) {
+      LOG(ERROR) << "Failed to synchronise with child process";
+      goto error;
     }
     close(pipe_fds[1]);
     return real_pid;
   }
 
  error:
   if (pid > 0) {
     if (waitpid(pid, NULL, WNOHANG) == -1)
       LOG(ERROR) << "Failed to wait for process";
   }
@@ skipping 121 matching lines @@
                                     PickleIterator iter) {
   if (HANDLE_EINTR(write(fd, &sandbox_flags_, sizeof(sandbox_flags_))) !=
                    sizeof(sandbox_flags_)) {
     PLOG(ERROR) << "write";
   }
 
   return false;
 }
 
 }  // namespace content