Changing multiprocess test SpawnChild to return a struct.

mojo/edk/test/multiprocess_test_helper.cc

Index: mojo/edk/test/multiprocess_test_helper.cc
diff --git a/mojo/edk/test/multiprocess_test_helper.cc b/mojo/edk/test/multiprocess_test_helper.cc
index 8eaccf08d6d63bcb4cec91bfc0074866d01ae207..8c6f5982d2ed09cea77f2eb98976440a8943cf8d 100644
--- a/mojo/edk/test/multiprocess_test_helper.cc
+++ b/mojo/edk/test/multiprocess_test_helper.cc
@@ -160,8 +160,9 @@ ScopedMessagePipeHandle MultiprocessTestHelper::StartChildWithExtraSwitch(
     pipe = ConnectToPeerProcess(std::move(server_handle), peer_token_);
   }
 
-  test_child_ =
+  base::SpawnChildResult result =
       base::SpawnMultiProcessTestChild(test_child_main, command_line, options);
+  test_child_ = std::move(result.process);
   if (launch_type == LaunchType::CHILD || launch_type == LaunchType::PEER)
     channel.ChildProcessLaunched();