mojo: Add ExistingThreadLoader.

content/common/mojo/existing_thread_loader.cc

+// Copyright 2016 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/common/mojo/existing_thread_loader.h"
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/location.h"
+#include "base/single_thread_task_runner.h"
+
+namespace content {
+
+ExistingThreadLoader::ExistingThreadLoader(
+    const ApplicationFactory& factory,
+    scoped_refptr<base::SingleThreadTaskRunner> task_runner)
+    : factory_(factory), task_runner_(task_runner), weak_factory_(this) {}
+
+ExistingThreadLoader::~ExistingThreadLoader() {}
+
+void ExistingThreadLoader::Load(const std::string& name,
+                               mojo::shell::mojom::ShellClientRequest request) {
+  task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&ExistingThreadLoader::LoadOnTaskRunner,
+                 weak_factory_.GetWeakPtr(), name, base::Passed(&request)));
+}
+
+void ExistingThreadLoader::LoadOnTaskRunner(
+    const std::string& name,
+    mojo::shell::mojom::ShellClientRequest request) {
+  if (!shell_client_) {
+    shell_client_ = factory_.Run();
+    factory_ = ApplicationFactory();

[alokp, 2016/04/05 15:33:55]

what is the need for clearing the fatory_?

+  }
+
+  connections_.push_back(make_scoped_ptr(
+      new mojo::ShellConnection(shell_client_.get(), std::move(request))));
+}
+
+}  // namespace content