ozone: fix HDPMLegacy - do the PF after overlays, also clear old overlays

ui/ozone/platform/dri/test/mock_dri_wrapper.h

Index: ui/ozone/platform/dri/test/mock_dri_wrapper.h
diff --git a/ui/ozone/platform/dri/test/mock_dri_wrapper.h b/ui/ozone/platform/dri/test/mock_dri_wrapper.h
index 9f64b75d82a95fcf6fce2b516330c271013cafe2..18c990f2df447713ad3ea067b6c994d623bb087a 100644
--- a/ui/ozone/platform/dri/test/mock_dri_wrapper.h
+++ b/ui/ozone/platform/dri/test/mock_dri_wrapper.h
@@ -37,6 +37,7 @@ class MockDriWrapper : public ui::DriWrapper {
   }
   int get_page_flip_call_count() const { return page_flip_call_count_; }
   int get_overlay_flip_call_count() const { return overlay_flip_call_count_; }
+  int get_overlay_clear_call_count() const { return overlay_clear_call_count_; }
   void fail_init() { fd_ = -1; }
   void set_set_crtc_expectation(bool state) { set_crtc_expectation_ = state; }
   void set_page_flip_expectation(bool state) { page_flip_expectation_ = state; }
@@ -110,6 +111,7 @@ class MockDriWrapper : public ui::DriWrapper {
   int remove_framebuffer_call_count_;
   int page_flip_call_count_;
   int overlay_flip_call_count_;
+  int overlay_clear_call_count_;
 
   bool set_crtc_expectation_;
   bool add_framebuffer_expectation_;