mojo: kill app_thread before unloading main app library and add tests

mojo/shell/in_process_dynamic_service_runner.h

Index: mojo/shell/in_process_dynamic_service_runner.h
diff --git a/mojo/shell/in_process_dynamic_service_runner.h b/mojo/shell/in_process_dynamic_service_runner.h
index ce6b029c782d5a0c6295f0449f27e4ca5b1214b0..f1fc9b3fce1cb4dc2bf254e8e5bd61df74b9aac2 100644
--- a/mojo/shell/in_process_dynamic_service_runner.h
+++ b/mojo/shell/in_process_dynamic_service_runner.h
@@ -8,6 +8,7 @@
 #include "base/callback.h"
 #include "base/files/file_path.h"
 #include "base/macros.h"
+#include "base/scoped_native_library.h"
 #include "base/threading/simple_thread.h"
 #include "mojo/shell/dynamic_service_runner.h"
 #include "mojo/shell/keep_alive.h"
@@ -38,6 +39,7 @@ class InProcessDynamicServiceRunner
   ScopedMessagePipeHandle service_handle_;
   base::Callback<bool(void)> app_completed_callback_runner_;
 
+  base::ScopedNativeLibrary app_library_;
   base::DelegateSimpleThread thread_;
 
   DISALLOW_COPY_AND_ASSIGN(InProcessDynamicServiceRunner);