Tag some of Mojo heap allocations for the heap profiler.

mojo/edk/system/multiprocess_message_pipe_unittest.cc

Index: mojo/edk/system/multiprocess_message_pipe_unittest.cc
diff --git a/mojo/edk/system/multiprocess_message_pipe_unittest.cc b/mojo/edk/system/multiprocess_message_pipe_unittest.cc
index 2ba0c3885c57018bc5248dfa2e1fe604dcaab7f7..498980c9d0e99db6fca826a10c11e6a63077a76c 100644
--- a/mojo/edk/system/multiprocess_message_pipe_unittest.cc
+++ b/mojo/edk/system/multiprocess_message_pipe_unittest.cc
@@ -1274,7 +1274,7 @@ DEFINE_TEST_CLIENT_TEST_WITH_PIPE(MessagePipeStatusChangeInTransitClient,
   // Wait on handle 1 using a Watcher.
   {
     base::RunLoop run_loop;
-    Watcher watcher;
+    Watcher watcher(FROM_HERE);
     watcher.Start(Handle(handles[1]), MOJO_HANDLE_SIGNAL_PEER_CLOSED,
                   base::Bind([] (base::RunLoop* loop, MojoResult result) {
                     EXPECT_EQ(MOJO_RESULT_OK, result);