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

services/service_manager/service_manager.cc

Index: services/service_manager/service_manager.cc
diff --git a/services/service_manager/service_manager.cc b/services/service_manager/service_manager.cc
index 99b9869ee5b99b844139621efe4698041b13fee5..ed5e3044994bf5a44ed47a9c89fa1d9020b5348a 100644
--- a/services/service_manager/service_manager.cc
+++ b/services/service_manager/service_manager.cc
@@ -322,7 +322,8 @@
     service.Bind(mojom::ServicePtrInfo(std::move(service_handle), 0));
     params->set_client_process_info(std::move(service),
                                     std::move(pid_receiver_request));
-    service_manager_->Connect(std::move(params), weak_factory_.GetWeakPtr());
+    service_manager_->Connect(
+        std::move(params), nullptr, weak_factory_.GetWeakPtr());
   }
 
   void Connect(const service_manager::Identity& in_target,
@@ -341,7 +342,8 @@
     params->set_target(target);
     params->set_remote_interfaces(std::move(remote_interfaces));
     params->set_connect_callback(callback);
-    service_manager_->Connect(std::move(params), weak_factory_.GetWeakPtr());
+    service_manager_->Connect(
+        std::move(params), nullptr, weak_factory_.GetWeakPtr());
   }
 
   void BindInterface(const service_manager::Identity& in_target,
@@ -362,7 +364,8 @@
     params->set_interface_request_info(interface_name,
                                        std::move(interface_pipe));
     params->set_bind_interface_callback(callback);
-    service_manager_->Connect(std::move(params), weak_factory_.GetWeakPtr());
+    service_manager_->Connect(
+        std::move(params), nullptr, weak_factory_.GetWeakPtr());
   }
 
   void Clone(mojom::ConnectorRequest request) override {
@@ -682,26 +685,22 @@
 }
 
 void ServiceManager::Connect(std::unique_ptr<ConnectParams> params) {
-  Connect(std::move(params), nullptr);
-}
-
-void ServiceManager::RegisterService(
-    const Identity& identity,
-    mojom::ServicePtr service,
-    mojom::PIDReceiverRequest pid_receiver_request) {
-  auto params = base::MakeUnique<ConnectParams>();
-
-  if (!pid_receiver_request.is_pending()) {
-    mojom::PIDReceiverPtr pid_receiver;
-    pid_receiver_request = mojom::PIDReceiverRequest(&pid_receiver);
-    pid_receiver->SetPID(base::Process::Current().Pid());
-  }
-
-  params->set_source(identity);
-  params->set_target(identity);
-  params->set_client_process_info(
-      std::move(service), std::move(pid_receiver_request));
-  Connect(std::move(params), nullptr);
+  Connect(std::move(params), nullptr, nullptr);
+}
+
+mojom::ServiceRequest ServiceManager::StartEmbedderService(
+    const std::string& name) {
+  std::unique_ptr<ConnectParams> params(new ConnectParams);
+
+  Identity embedder_identity(name, mojom::kRootUserID);
+  params->set_source(embedder_identity);
+  params->set_target(embedder_identity);
+
+  mojom::ServicePtr service;
+  mojom::ServiceRequest request(&service);
+  Connect(std::move(params), std::move(service), nullptr);
+
+  return request;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -766,6 +765,7 @@
 }
 
 void ServiceManager::Connect(std::unique_ptr<ConnectParams> params,
+                             mojom::ServicePtr service,
                              base::WeakPtr<Instance> source_instance) {
   TRACE_EVENT_INSTANT1("service_manager", "ServiceManager::Connect",
                        TRACE_EVENT_SCOPE_THREAD, "original_name",
@@ -773,11 +773,10 @@
   DCHECK(!params->target().name().empty());
   DCHECK(base::IsValidGUID(params->target().user_id()));
   DCHECK_NE(mojom::kInheritUserID, params->target().user_id());
-  DCHECK(!params->HasClientProcessInfo() ||
-         !identity_to_instance_.count(params->target()));
+  DCHECK(!service.is_bound() || !identity_to_instance_.count(params->target()));
 
   // Connect to an existing matching instance, if possible.
-  if (!params->HasClientProcessInfo() && ConnectToExistingInstance(&params))
+  if (!service.is_bound() && ConnectToExistingInstance(&params))
     return;
 
   // The catalog needs to see the source identity as that of the originating
@@ -792,7 +791,7 @@
       name,
       base::Bind(&service_manager::ServiceManager::OnGotResolvedName,
                  weak_ptr_factory_.GetWeakPtr(), base::Passed(&params),
-                 !!source_instance, source_instance));
+                 base::Passed(&service), !!source_instance, source_instance));
 }
 
 ServiceManager::Instance* ServiceManager::GetExistingInstance(
@@ -933,6 +932,7 @@
 }
 
 void ServiceManager::OnGotResolvedName(std::unique_ptr<ConnectParams> params,
+                                       mojom::ServicePtr service,
                                        bool has_source_instance,
                                        base::WeakPtr<Instance> source_instance,
                                        mojom::ResolveResultPtr result,
@@ -992,8 +992,12 @@
 
   // Below are various paths through which a new Instance can be bound to a
   // Service proxy.
-  if (params->HasClientProcessInfo()) {
-    // This branch should be reachable only via a call to RegisterService() . We
+  if (service.is_bound()) {
+    // If a ServicePtr was provided, there's no more work to do: someone
+    // is already holding a corresponding ServiceRequest.
+    instance->StartWithService(std::move(service));
+  } else if (params->HasClientProcessInfo()) {
+    // This branch should be reachable only via a call to RegisterService(). We
     // start the instance but return early before we connect to it. Clients will
     // call Connect() with the target identity subsequently.
     instance->BindPIDReceiver(params->TakePIDReceiverRequest());
@@ -1001,7 +1005,6 @@
     return;
   } else {
     // Otherwise we create a new Service pipe.
-    mojom::ServicePtr service;
     mojom::ServiceRequest request(&service);
 
     // The catalog was unable to read a manifest for this service. We can't do