Mojo EDK: Add safe process connection API

mojo/edk/embedder/pending_process_connection.cc

Index: mojo/edk/embedder/pending_process_connection.cc
diff --git a/mojo/edk/embedder/pending_process_connection.cc b/mojo/edk/embedder/pending_process_connection.cc
new file mode 100644
index 0000000000000000000000000000000000000000..8ab58727931f98a93f77735ac6eb37b654ada07b
--- /dev/null
+++ b/mojo/edk/embedder/pending_process_connection.cc
@@ -0,0 +1,50 @@
+// Copyright 2017 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 "mojo/edk/embedder/pending_process_connection.h"
+
+#include "mojo/edk/embedder/embedder.h"
+#include "mojo/edk/embedder/embedder_internal.h"
+#include "mojo/edk/system/core.h"
+
+namespace mojo {
+namespace edk {
+
+PendingProcessConnection::PendingProcessConnection()
+    : process_token_(GenerateRandomToken()) {
+  DCHECK(internal::g_core);
+}
+
+PendingProcessConnection::~PendingProcessConnection() {
+  if (has_message_pipes_ && !connected_) {
+    DCHECK(internal::g_core);
+    internal::g_core->ChildLaunchFailed(process_token_);
+  }
+}
+
+ScopedMessagePipeHandle PendingProcessConnection::CreateMessagePipe(
+    std::string* token) {
+  has_message_pipes_ = true;
+  DCHECK(internal::g_core);
+  *token = GenerateRandomToken();
+  return internal::g_core->CreateParentMessagePipe(*token, process_token_);
+}
+
+void PendingProcessConnection::Connect(
+    base::ProcessHandle process,
+    ScopedPlatformHandle channel,
+    const ProcessErrorCallback& error_callback) {
+  // It's now safe to avoid cleanup in the destructor, as the lifetime of any
+  // associated resources is effectively bound to the |channel| passed to
+  // AddChild() below.
+  DCHECK(!connected_);
+  connected_ = true;
+
+  DCHECK(internal::g_core);
+  internal::g_core->AddChild(process, std::move(channel), process_token_,
+                             error_callback);
+}
+
+}  // namespace edk
+}  // namespace mojo