Mojo EDK: Add safe process connection API

remoting/host/win/wts_session_process_delegate.cc

Index: remoting/host/win/wts_session_process_delegate.cc
diff --git a/remoting/host/win/wts_session_process_delegate.cc b/remoting/host/win/wts_session_process_delegate.cc
index 635bd04b68dadb4923ac4a836a2add44aba5847e..c665a59c4571a3ce7ecce4adc4a9a623fe2d7d36 100644
--- a/remoting/host/win/wts_session_process_delegate.cc
+++ b/remoting/host/win/wts_session_process_delegate.cc
@@ -7,6 +7,7 @@
 
 #include "remoting/host/win/wts_session_process_delegate.h"
 
+#include <memory>
 #include <utility>
 
 #include "base/bind.h"
@@ -27,6 +28,7 @@
 #include "ipc/ipc_message.h"
 #include "mojo/edk/embedder/embedder.h"
 #include "mojo/edk/embedder/named_platform_channel_pair.h"
+#include "mojo/edk/embedder/pending_process_connection.h"
 #include "mojo/edk/embedder/platform_channel_pair.h"
 #include "mojo/edk/embedder/platform_handle_utils.h"
 #include "mojo/edk/embedder/scoped_platform_handle.h"
@@ -155,8 +157,8 @@ class WtsSessionProcessDelegate::Core
   // Tracks the id of the worker process.
   base::ProcessId worker_process_pid_ = base::kNullProcessId;
 
-  // The mojo child token for the process being launched.
-  std::string mojo_child_token_;
+  // The pending process connection for the process being launched.
+  std::unique_ptr<mojo::edk::PendingProcessConnection> process_connection_;
 
   DISALLOW_COPY_AND_ASSIGN(Core);
 };
@@ -257,10 +259,7 @@ void WtsSessionProcessDelegate::Core::CloseChannel() {
   channel_.reset();
   elevated_server_handle_.reset();
   elevated_launcher_pid_ = base::kNullProcessId;
-  if (!mojo_child_token_.empty()) {
-    mojo::edk::ChildProcessLaunchFailed(mojo_child_token_);
-    mojo_child_token_.clear();
-  }
+  process_connection_.reset();
 }
 
 void WtsSessionProcessDelegate::Core::KillProcess() {
@@ -391,14 +390,12 @@ void WtsSessionProcessDelegate::Core::DoLaunchProcess() {
                                   target_command_->GetProgram());
   }
 
-  const std::string mojo_message_pipe_token = mojo::edk::GenerateRandomToken();
-  mojo_child_token_ = mojo::edk::GenerateRandomToken();
+  std::string mojo_pipe_token;
+  process_connection_ = base::MakeUnique<mojo::edk::PendingProcessConnection>();
   std::unique_ptr<IPC::ChannelProxy> channel = IPC::ChannelProxy::Create(
-      mojo::edk::CreateParentMessagePipe(mojo_message_pipe_token,
-                                         mojo_child_token_)
-          .release(),
+      process_connection_->CreateMessagePipe(&mojo_pipe_token).release(),
       IPC::Channel::MODE_SERVER, this, io_task_runner_);
-  command_line.AppendSwitchASCII(kMojoPipeToken, mojo_message_pipe_token);
+  command_line.AppendSwitchASCII(kMojoPipeToken, mojo_pipe_token);
 
   std::unique_ptr<mojo::edk::PlatformChannelPair> normal_mojo_channel;
   std::unique_ptr<mojo::edk::NamedPlatformChannelPair> elevated_mojo_channel;
@@ -558,10 +555,8 @@ void WtsSessionProcessDelegate::Core::ReportProcessLaunched(
   DCHECK(caller_task_runner_->BelongsToCurrentThread());
   DCHECK(!worker_process_.IsValid());
 
-  mojo::edk::ChildProcessLaunched(worker_process.Get(),
-                                  std::move(server_handle),
-                                  mojo_child_token_);
-  mojo_child_token_.clear();
+  process_connection_->Connect(worker_process.Get(), std::move(server_handle));
+  process_connection_.reset();
   worker_process_ = std::move(worker_process);
 
   // Report a handle that can be used to wait for the worker process completion,