Refactor NaClProcessHost. Reduce chances to leak the resource.

components/nacl/renderer/ppb_nacl_private_impl.cc

Index: components/nacl/renderer/ppb_nacl_private_impl.cc
diff --git a/components/nacl/renderer/ppb_nacl_private_impl.cc b/components/nacl/renderer/ppb_nacl_private_impl.cc
index c879e48671bf9e1cb00fc42c3325ba6d162bf16f..8320f907c62dfd1affec475b04a9c41c7ba32f81 100644
--- a/components/nacl/renderer/ppb_nacl_private_impl.cc
+++ b/components/nacl/renderer/ppb_nacl_private_impl.cc
@@ -385,7 +385,6 @@ void LaunchSelLdr(PP_Instance instance,
   scoped_ptr<ManifestServiceChannel::Delegate> manifest_service_proxy(
       new ManifestServiceProxy(instance, process_type));
 
-  FileDescriptor result_socket;
   IPC::Sender* sender = content::RenderThread::Get();
   DCHECK(sender);
   int routing_id = GetRoutingID(instance);
@@ -482,7 +481,7 @@ void LaunchSelLdr(PP_Instance instance,
                    static_cast<int32_t>(PP_ERROR_FAILED)));
     return;
   }
-  result_socket = launch_result.imc_channel_handle;
+
   instance_info.channel_handle = launch_result.ppapi_ipc_channel_handle;
   instance_info.plugin_pid = launch_result.plugin_pid;
   instance_info.plugin_child_id = launch_result.plugin_child_id;
@@ -493,7 +492,9 @@ void LaunchSelLdr(PP_Instance instance,
     nacl_plugin_instance->instance_info.reset(new InstanceInfo(instance_info));
   }
 
-  *(static_cast<NaClHandle*>(imc_handle)) = ToNativeHandle(result_socket);
+  *(static_cast<NaClHandle*>(imc_handle)) =
+      IPC::PlatformFileForTransitToPlatformFile(
+          launch_result.imc_channel_handle);
 
   // Store the crash information shared memory handle.
   load_manager->set_crash_info_shmem_handle(