Correct process id for sandbox'd trace events.

content/browser/zygote_main_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/browser/zygote_host_impl_linux.h"
 
 #include <dlfcn.h>
 #include <fcntl.h>
 #include <pthread.h>
 #include <stdio.h>
 #include <sys/socket.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <unistd.h>
 
 #include "base/basictypes.h"
 #include "base/command_line.h"
+#include "base/debug/trace_event.h"
 #include "base/eintr_wrapper.h"
 #include "base/file_path.h"
 #include "base/file_util.h"
 #include "base/global_descriptors_posix.h"
 #include "base/hash_tables.h"
 #include "base/linux_util.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/pickle.h"
 #include "base/process_util.h"
 #include "base/rand_util.h"
@@ skipping 291 matching lines @@
                                  sizeof(real_pid))) {
         LOG(FATAL) << "Failed to synchronise with parent zygote process";
       }
       if (real_pid <= 0) {
         LOG(FATAL) << "Invalid pid from parent zygote";
       }
 #if defined(OS_LINUX)
       // Sandboxed processes need to send the global, non-namespaced PID when
       // setting up an IPC channel to their parent.
       IPC::Channel::SetGlobalPid(real_pid);
+      // Force the real PID so chrome event data have a PID that corresponds
+      // to system trace event data.
+      base::debug::TraceLog::GetInstance()->SetProcessID(
+          static_cast<int>(real_pid));

[Markus (顧孟勤), 2012/04/20 21:13:29]

You mentioned that this is currently something that is only need for CrOS. Just
double-checking that you verified the code is harmless on non-CrOS builds for
OS_LINUX.

Other than that, this change looks fine to me. Glad to see that it is a
relatively simple and well-contained change. Of course, computing thread ids is
going to be a little more challenging.

 #endif
       close(pipe_fds[0]);
       close(dummy_fd);
       return 0;
     } else {
       // In the parent process.
       close(dummy_fd);
       dummy_fd = -1;
       close(pipe_fds[0]);
       pipe_fds[0] = -1;
@@ skipping 658 matching lines @@
       VLOG(1) << "Enabling experimental Seccomp sandbox.";
       sandbox_flags |= ZygoteHostImpl::kSandboxSeccomp;
     }
   }
 #endif  // SECCOMP_SANDBOX
 
   Zygote zygote(sandbox_flags, forkdelegate);
   // This function call can return multiple times, once per fork().
   return zygote.ProcessRequests();
 }