Add DVLOG with child process id in mojo shell.

services/shell/runner/host/child_process_host.cc

Index: services/shell/runner/host/child_process_host.cc
diff --git a/services/shell/runner/host/child_process_host.cc b/services/shell/runner/host/child_process_host.cc
index 30195b5404f6da9fc8c06e5386c1f7ecddb4a20b..d8ee28818a82604a2cf880fc2a55f4ca607be6b8 100644
--- a/services/shell/runner/host/child_process_host.cc
+++ b/services/shell/runner/host/child_process_host.cc
@@ -199,6 +199,11 @@ void ChildProcessHost::DoLaunch(
   }
 
   if (child_process_.IsValid()) {
+    DVLOG(0) << "Launched child process pid=" << child_process_.Pid()
+             << ", instance=" << target_.instance()
+             << ", name=" << target_.name()
+             << ", user_id=" << target_.user_id();
+
     if (mojo_ipc_channel_.get()) {
       mojo_ipc_channel_->ChildProcessLaunched();
       mojo::edk::ChildProcessLaunched(