dbus: Add comments about the right way to expose methods

dbus/test_service.cc

 // Copyright (c) 2012 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 "dbus/test_service.h"
 
 #include "base/bind.h"
 #include "base/test/test_timeouts.h"
 #include "base/threading/platform_thread.h"
 #include "dbus/bus.h"
@@ skipping 20 matching lines @@
     : request_ownership_options(Bus::REQUIRE_PRIMARY) {
 }
 
 TestService::Options::~Options() {
 }
 
 TestService::TestService(const Options& options)
     : base::Thread("TestService"),
       request_ownership_options_(options.request_ownership_options),
       dbus_task_runner_(options.dbus_task_runner),
-      on_all_methods_exported_(false, false),
+      on_name_obtained_(false, false),
       num_exported_methods_(0) {
 }
 
 TestService::~TestService() {
   Stop();
 }
 
 bool TestService::StartService() {
   base::Thread::Options thread_options;
   thread_options.message_loop_type = base::MessageLoop::TYPE_IO;
   return StartWithOptions(thread_options);
 }
 
 bool TestService::WaitUntilServiceIsStarted() {
   const base::TimeDelta timeout(TestTimeouts::action_max_timeout());
-  // Wait until all methods are exported.
-  return on_all_methods_exported_.TimedWait(timeout);
+  // Wait until the ownership of the service name is obtained.
+  return on_name_obtained_.TimedWait(timeout);
 }
 
 void TestService::ShutdownAndBlock() {
   message_loop()->PostTask(
       FROM_HERE,
       base::Bind(&TestService::ShutdownAndBlockInternal,
                  base::Unretained(this)));
 }
 
 bool TestService::HasDBusThread() {
@@ skipping 62 matching lines @@
                                     base::Unretained(this),
                                     callback));
 }
 
 void TestService::OnOwnership(base::Callback<void(bool)> callback,
                               const std::string& service_name,
                               bool success) {
   has_ownership_ = success;
   LOG_IF(ERROR, !success) << "Failed to own: " << service_name;
   callback.Run(success);
+
+  on_name_obtained_.Signal();
 }
 
 void TestService::OnExported(const std::string& interface_name,
                              const std::string& method_name,
                              bool success) {
   if (!success) {
     LOG(ERROR) << "Failed to export: " << interface_name << "."
                << method_name;
     // Returning here will make WaitUntilServiceIsStarted() to time out
     // and return false.
     return;
   }
 
   ++num_exported_methods_;
-  if (num_exported_methods_ == kNumMethodsToExport)
-    on_all_methods_exported_.Signal();
+  if (num_exported_methods_ == kNumMethodsToExport) {
+    // As documented in exported_object.h, the service name should be
+    // requested after all methods are exposed.
+    bus_->RequestOwnership("org.chromium.TestService",
+                           request_ownership_options_,
+                           base::Bind(&TestService::OnOwnership,
+                                      base::Unretained(this),
+                                      base::Bind(&EmptyCallback)));
+  }
 }
 
 void TestService::Run(base::MessageLoop* message_loop) {
   Bus::Options bus_options;
   bus_options.bus_type = Bus::SESSION;
   bus_options.connection_type = Bus::PRIVATE;
   bus_options.dbus_task_runner = dbus_task_runner_;
   bus_ = new Bus(bus_options);
 
-  bus_->RequestOwnership("org.chromium.TestService",
-                         request_ownership_options_,
-                         base::Bind(&TestService::OnOwnership,
-                                    base::Unretained(this),
-                                    base::Bind(&EmptyCallback)));
-
   exported_object_ = bus_->GetExportedObject(
       ObjectPath("/org/chromium/TestObject"));
 
   int num_methods = 0;
   exported_object_->ExportMethod(
       "org.chromium.TestInterface",
       "Echo",
       base::Bind(&TestService::Echo,
                  base::Unretained(this)),
       base::Bind(&TestService::OnExported,
@@ skipping 425 matching lines @@
   array_writer.OpenDictEntry(&dict_entry_writer);
   dict_entry_writer.AppendString("Name");
   dict_entry_writer.AppendVariantOfString(name);
   array_writer.CloseContainer(&dict_entry_writer);
   writer.CloseContainer(&array_writer);
 
   exported_object_->SendSignal(&signal);
 }
 
 }  // namespace dbus