Backfill some UI tests.

content/test/test_render_view_host.h

Index: content/test/test_render_view_host.h
diff --git a/content/test/test_render_view_host.h b/content/test/test_render_view_host.h
index 9bbee7414f7423d21581dbee832ec0eddc195e40..faefdcc8a450b6d0e86393e6ac8127444087b7bb 100644
--- a/content/test/test_render_view_host.h
+++ b/content/test/test_render_view_host.h
@@ -123,6 +123,9 @@ class TestRenderWidgetHostView : public RenderWidgetHostViewBase {
   void reset_did_change_compositor_frame_sink() {
     did_change_compositor_frame_sink_ = false;
   }
+  void set_native_view(gfx::NativeView native_view) {
+    native_view_ = native_view;
+  }
 
  protected:
   RenderWidgetHostImpl* rwh_;
@@ -135,6 +138,7 @@ class TestRenderWidgetHostView : public RenderWidgetHostViewBase {
   bool did_change_compositor_frame_sink_ = false;
   SkColor background_color_;
   ui::DummyTextInputClient text_input_client_;
+  gfx::NativeView native_view_ = nullptr;
 };
 
 #if defined(COMPILER_MSVC)