Mojo: Log an error on the remote message pipe leak condition.[1]

mojo/system/remote_message_pipe_unittest.cc

Index: mojo/system/remote_message_pipe_unittest.cc
diff --git a/mojo/system/remote_message_pipe_unittest.cc b/mojo/system/remote_message_pipe_unittest.cc
index e3bff2b0549b7711e5213a8bd981f49adac74879..45d757a39b65cdd72290bf4800f71d2b5110df50 100644
--- a/mojo/system/remote_message_pipe_unittest.cc
+++ b/mojo/system/remote_message_pipe_unittest.cc
@@ -366,6 +366,11 @@ TEST_F(RemoteMessagePipeTest, Multiplex) {
                              MOJO_READ_MESSAGE_FLAG_NONE));
   EXPECT_EQ(sizeof(world), static_cast<size_t>(buffer_size));
   EXPECT_STREQ(world, buffer);
+
+  mp0->Close(0);
+  mp1->Close(1);
+  mp2->Close(0);
+  mp3->Close(1);
 }
 
 TEST_F(RemoteMessagePipeTest, CloseBeforeConnect) {