Ensure that NativeViewport destructs correctly on Linux.

components/native_viewport/native_viewport_application_delegate.h

Index: components/native_viewport/native_viewport_application_delegate.h
diff --git a/components/native_viewport/native_viewport_application_delegate.h b/components/native_viewport/native_viewport_application_delegate.h
index 4584ffff05b837f38d86c023d7d7d2019f936fe9..e95bf2066a15be69277d5dfbce8b2ea5fad13012 100644
--- a/components/native_viewport/native_viewport_application_delegate.h
+++ b/components/native_viewport/native_viewport_application_delegate.h
@@ -17,6 +17,10 @@ class ApplicationConnection;
 class ApplicationImpl;
 }
 
+namespace ui {
+class PlatformEventSource;
+}
+
 namespace native_viewport {
 
 class NativeViewportApplicationDelegate
@@ -42,6 +46,7 @@ class NativeViewportApplicationDelegate
               mojo::InterfaceRequest<mojo::Gpu> request) override;
 
   scoped_refptr<gles2::GpuState> gpu_state_;
+  scoped_ptr<ui::PlatformEventSource> event_source_;
   bool is_headless_;
   mojo::TracingImpl tracing_;