Revert of [Service Manager] Get rid of dynamic service discovery

services/service_manager/background/background_service_manager.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 "services/service_manager/background/background_service_manager.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
-#include "base/memory/ref_counted.h"
 #include "base/message_loop/message_pump_default.h"
 #include "base/path_service.h"
 #include "base/run_loop.h"
-#include "base/sequenced_task_runner.h"
 #include "base/single_thread_task_runner.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/threading/simple_thread.h"
 #include "services/catalog/store.h"
 #include "services/service_manager/connect_params.h"
 #include "services/service_manager/public/cpp/service.h"
 #include "services/service_manager/public/cpp/service_context.h"
 #include "services/service_manager/service_manager.h"
 #include "services/service_manager/standalone/context.h"
 
 namespace service_manager {
 
-BackgroundServiceManager::BackgroundServiceManager(
-    service_manager::ServiceProcessLauncher::Delegate* launcher_delegate,
-    std::unique_ptr<base::Value> catalog_contents)
-    : background_thread_("service_manager") {
-  background_thread_.Start();
-  background_thread_.task_runner()->PostTask(
-      FROM_HERE,
-      base::Bind(&BackgroundServiceManager::InitializeOnBackgroundThread,
-                 base::Unretained(this), launcher_delegate,
-                 base::Passed(&catalog_contents)));
+namespace {
+
+std::unique_ptr<base::MessagePump> CreateDefaultMessagePump() {
+  return base::WrapUnique(new base::MessagePumpDefault);
 }
 
+class MojoMessageLoop : public base::MessageLoop {
+ public:
+  MojoMessageLoop()
+      : base::MessageLoop(base::MessageLoop::TYPE_CUSTOM,
+                          base::Bind(&CreateDefaultMessagePump)) {}
+  ~MojoMessageLoop() override {}
+
+  void BindToCurrentThread() { base::MessageLoop::BindToCurrentThread(); }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(MojoMessageLoop);
+};
+
+}  // namespace
+
+// Manages the thread to startup mojo.
+class BackgroundServiceManager::MojoThread : public base::SimpleThread {
+ public:
+  explicit MojoThread(
+      std::unique_ptr<BackgroundServiceManager::InitParams> init_params)
+      : SimpleThread("background-service-manager"),
+        init_params_(std::move(init_params)) {}
+  ~MojoThread() override {}
+
+  void CreateServiceRequest(base::WaitableEvent* signal,
+                            const std::string& name,
+                            mojom::ServiceRequest* request) {
+    // Only valid to call this on the background thread.
+    DCHECK(message_loop_->task_runner()->BelongsToCurrentThread());
+    *request = context_->service_manager()->StartEmbedderService(name);
+    signal->Signal();
+  }
+
+  void Connect(std::unique_ptr<ConnectParams> params) {
+    context_->service_manager()->Connect(std::move(params));
+  }
+
+  base::MessageLoop* message_loop() { return message_loop_; }
+
+  // Stops the background thread.
+  void Stop() {
+    DCHECK_NE(message_loop_, base::MessageLoop::current());
+    message_loop_->task_runner()->PostTask(
+        FROM_HERE, base::MessageLoop::QuitWhenIdleClosure());
+    Join();
+  }
+
+  void RunServiceManagerCallback(
+      const BackgroundServiceManager::ServiceManagerThreadCallback& callback) {
+    DCHECK(message_loop_->task_runner()->BelongsToCurrentThread());
+    callback.Run(context_->service_manager());
+  }
+
+  // base::SimpleThread:
+  void Start() override {
+    DCHECK(!message_loop_);
+    message_loop_ = new MojoMessageLoop;
+    base::SimpleThread::Start();
+  }
+  void Run() override {
+    // The construction/destruction order is very finicky and has to be done
+    // in the order here.
+    std::unique_ptr<base::MessageLoop> message_loop(message_loop_);
+
+    std::unique_ptr<Context::InitParams> context_init_params(
+        new Context::InitParams);
+    if (init_params_) {
+      context_init_params->service_process_launcher_delegate =
+          init_params_->service_process_launcher_delegate;
+      context_init_params->init_edk = init_params_->init_edk;
+    }
+    if (context_init_params->init_edk)
+      Context::EnsureEmbedderIsInitialized();
+
+    message_loop_->BindToCurrentThread();
+
+    std::unique_ptr<Context> context(new Context);
+    context_ = context.get();
+    context_->Init(std::move(context_init_params));
+
+    base::RunLoop().Run();
+
+    // Has to happen after run, but while messageloop still valid.
+    context_->Shutdown();
+
+    // Context has to be destroyed after the MessageLoop has been destroyed.
+    message_loop.reset();
+    context_ = nullptr;
+  }
+
+ private:
+  // We own this. It's created on the main thread, but destroyed on the
+  // background thread.
+  MojoMessageLoop* message_loop_ = nullptr;
+  // Created in Run() on the background thread.
+  Context* context_ = nullptr;
+
+  std::unique_ptr<BackgroundServiceManager::InitParams> init_params_;
+
+  DISALLOW_COPY_AND_ASSIGN(MojoThread);
+};
+
+BackgroundServiceManager::InitParams::InitParams() {}
+BackgroundServiceManager::InitParams::~InitParams() {}
+
+BackgroundServiceManager::BackgroundServiceManager() {}
+
 BackgroundServiceManager::~BackgroundServiceManager() {
-  base::WaitableEvent done_event(
-      base::WaitableEvent::ResetPolicy::MANUAL,
-      base::WaitableEvent::InitialState::NOT_SIGNALED);
-  background_thread_.task_runner()->PostTask(
-      FROM_HERE,
-      base::Bind(&BackgroundServiceManager::ShutDownOnBackgroundThread,
-                 base::Unretained(this), &done_event));
-  done_event.Wait();
-  DCHECK(!context_);
+  thread_->Stop();
 }
 
-void BackgroundServiceManager::RegisterService(
-    const Identity& identity,
-    mojom::ServicePtr service,
-    mojom::PIDReceiverRequest pid_receiver_request) {
-  mojom::ServicePtrInfo service_info = service.PassInterface();
-  background_thread_.task_runner()->PostTask(
-      FROM_HERE,
-      base::Bind(&BackgroundServiceManager::RegisterServiceOnBackgroundThread,
-                 base::Unretained(this), identity, base::Passed(&service_info),
-                 base::Passed(&pid_receiver_request)));
+void BackgroundServiceManager::Init(std::unique_ptr<InitParams> init_params) {
+  DCHECK(!thread_);
+  thread_.reset(new MojoThread(std::move(init_params)));
+  thread_->Start();
 }
 
-void BackgroundServiceManager::InitializeOnBackgroundThread(
-    service_manager::ServiceProcessLauncher::Delegate* launcher_delegate,
-    std::unique_ptr<base::Value> catalog_contents) {
-  context_ =
-      base::MakeUnique<Context>(launcher_delegate, std::move(catalog_contents));
+mojom::ServiceRequest BackgroundServiceManager::CreateServiceRequest(
+    const std::string& name) {
+  std::unique_ptr<ConnectParams> params(new ConnectParams);
+  params->set_source(CreateServiceManagerIdentity());
+  params->set_target(Identity(name, mojom::kRootUserID));
+  mojom::ServiceRequest request;
+  base::WaitableEvent signal(base::WaitableEvent::ResetPolicy::MANUAL,
+                             base::WaitableEvent::InitialState::NOT_SIGNALED);
+  thread_->message_loop()->task_runner()->PostTask(
+      FROM_HERE,
+      base::Bind(&MojoThread::CreateServiceRequest,
+                 base::Unretained(thread_.get()), &signal, name, &request));
+  signal.Wait();
+  thread_->message_loop()->task_runner()->PostTask(
+      FROM_HERE,
+      base::Bind(&MojoThread::Connect, base::Unretained(thread_.get()),
+                 base::Passed(&params)));
+  return request;
 }
 
-void BackgroundServiceManager::ShutDownOnBackgroundThread(
-    base::WaitableEvent* done_event) {
-  context_.reset();
-  done_event->Signal();
-}
-
-void BackgroundServiceManager::RegisterServiceOnBackgroundThread(
-    const Identity& identity,
-    mojom::ServicePtrInfo service_info,
-    mojom::PIDReceiverRequest pid_receiver_request) {
-  mojom::ServicePtr service;
-  service.Bind(std::move(service_info));
-  context_->service_manager()->RegisterService(
-      identity, std::move(service), std::move(pid_receiver_request));
+void BackgroundServiceManager::ExecuteOnServiceManagerThread(
+    const ServiceManagerThreadCallback& callback) {
+  thread_->message_loop()->task_runner()->PostTask(
+      FROM_HERE, base::Bind(&MojoThread::RunServiceManagerCallback,
+                            base::Unretained(thread_.get()), callback));
 }
 
 }  // namespace service_manager