Make --wait-for-debugger work for mandoline launcher process.

mandoline/app/desktop/main.cc

Index: mandoline/app/desktop/main.cc
diff --git a/mandoline/app/desktop/main.cc b/mandoline/app/desktop/main.cc
index 2e635b39cf83c08b1784e81aa6e2e56d6e1448fc..8048bafa7a2bee2297b8080c540d3373ec97844f 100644
--- a/mandoline/app/desktop/main.cc
+++ b/mandoline/app/desktop/main.cc
@@ -14,6 +14,7 @@ int main(int argc, char** argv) {
   base::CommandLine::Init(argc, argv);
 
   mojo::runner::InitializeLogging();
+  mojo::runner::WaitForDebuggerIfNecessary();
 
   const base::CommandLine& command_line =
       *base::CommandLine::ForCurrentProcess();