Making Mandoline apps notice when all the objects they vended are gone so that it can terminate.

mojo/application/app_lifetime_helper.cc

Index: mojo/application/app_lifetime_helper.cc
diff --git a/mojo/application/app_lifetime_helper.cc b/mojo/application/app_lifetime_helper.cc
new file mode 100644
index 0000000000000000000000000000000000000000..cf0f5326f404352788f608945cde65e2e19d188f
--- /dev/null
+++ b/mojo/application/app_lifetime_helper.cc
@@ -0,0 +1,88 @@
+// Copyright 2015 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/application/app_lifetime_helper.h"
+
+#include "base/bind.h"
+#include "base/message_loop/message_loop.h"
+#include "mojo/application/public/cpp/application_impl.h"
+
+namespace mojo {
+
+AppRefCount::AppRefCount(
+    AppLifetimeHelper* app_lifetime_helper,
+    scoped_refptr<base::SingleThreadTaskRunner> app_task_runner)
+    : app_lifetime_helper_(app_lifetime_helper),
+      app_task_runner_(app_task_runner) {
+}
+
+AppRefCount::~AppRefCount() {
+#ifndef NDEBUG
+  // Ensure that this object is used on only one thread at a time, or else there
+  // could be races where the object is being reset on one thread and cloned on
+  // another.
+  if (clone_task_runner_) {
+    DCHECK(clone_task_runner_->BelongsToCurrentThread());
+  }
+#endif
+
+  if (app_task_runner_->BelongsToCurrentThread()) {
+    app_lifetime_helper_->Release();
+    return;
+  }
+
+  app_task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&AppLifetimeHelper::Release,
+                 base::Unretained(app_lifetime_helper_)));
+}
+
+scoped_ptr<AppRefCount> AppRefCount::Clone() {
+  if (app_task_runner_->BelongsToCurrentThread()) {
+    app_lifetime_helper_->AddRef();
+  } else {
+    app_task_runner_->PostTask(
+        FROM_HERE,
+        base::Bind(&AppLifetimeHelper::AddRef,
+                   base::Unretained(app_lifetime_helper_)));
+  }
+
+#ifndef NDEBUG
+  // Ensure that this object is used on only one thread at a time, or else there
+  // could be races where the object is being reset on one thread and cloned on
+  // another.
+  if (clone_task_runner_) {
+    DCHECK(clone_task_runner_->BelongsToCurrentThread());
+  } else {
+    clone_task_runner_ = base::MessageLoop::current()->task_runner();
+  }
+#endif
+
+  return make_scoped_ptr(new AppRefCount(
+      app_lifetime_helper_, app_task_runner_));
+}
+
+AppLifetimeHelper::AppLifetimeHelper()
+    : ref_count_(0) {
+}
+
+AppLifetimeHelper::~AppLifetimeHelper() {
+}
+
+scoped_ptr<AppRefCount> AppLifetimeHelper::CreateAppRefCount() {
+  AddRef();
+  return make_scoped_ptr(new AppRefCount(
+      this, base::MessageLoop::current()->task_runner()));
+}
+
+void AppLifetimeHelper::AddRef() {
+  ref_count_++;
+}
+
+void AppLifetimeHelper::Release() {
+  if (!--ref_count_)
+    ApplicationImpl::Terminate();
+}
+
+}  // namespace mojo