viz : Update damage tracking for underlays

Make sure to damage the previous underlay area
when switching underlays so that it is repainted.

BUG=854790
TEST=UnderlayTest.UpdateDamageWhenChangingUnderlays

Change-Id: Idec0e30e0cf65e4937f85dfd3bdfd9ba4120d5fe
Reviewed-on: https://chromium-review.googlesource.com/1161393
Commit-Queue: Fritz Koenig <frkoenig@chromium.org>
Reviewed-by: Daniele Castagna <dcastagna@chromium.org>
Cr-Commit-Position: refs/heads/master@{#580957}

components/viz/service/display/overlay_processor.cc

@@ -189,8 +189,7 @@ void OverlayProcessor::ProcessForOverlays(
 // Also subtract unoccluded underlays from the damage rect if we know that the
 // same underlay was scheduled on the previous frame. If the renderer decides
 // not to swap the framebuffer there will still be a transparent hole in the
-// previous frame. This only handles the common case of a single underlay quad
-// for fullscreen video.
+// previous frame.
 void OverlayProcessor::UpdateDamageRect(
     OverlayCandidateList* candidates,
     const gfx::Rect& previous_frame_underlay_rect,
@@ -209,13 +208,26 @@ void OverlayProcessor::UpdateDamageRect(
         if (overlay.is_opaque)
           damage_rect->Subtract(overlay_display_rect);
       }
-    } else if (overlay.is_unoccluded && this_frame_underlay_rect.IsEmpty()) {
+    } else if (this_frame_underlay_rect.IsEmpty()) {
+      // Process underlay candidates:
+      // Track the underlay_rect from frame to frame.  If it is the same
+      // and nothing is on top of it then that rect doesn't need to
+      // be damaged because the drawing is occurring on a different plane.
+      // If it is different then that indicates that a different underlay
+      // has been chosen and the previous underlay rect should be damaged
+      // because it has changed planes from the underlay plane to the
+      // main plane.
       this_frame_underlay_rect = ToEnclosedRect(overlay.display_rect);
+      if ((this_frame_underlay_rect == previous_frame_underlay_rect) &&
+          overlay.is_unoccluded) {
+        damage_rect->Subtract(this_frame_underlay_rect);
+      }
     }
   }
 
-  if (this_frame_underlay_rect == previous_frame_underlay_rect)
-    damage_rect->Subtract(this_frame_underlay_rect);
+  if (this_frame_underlay_rect != previous_frame_underlay_rect)
+    damage_rect->Union(previous_frame_underlay_rect);
+
   previous_frame_underlay_rect_ = this_frame_underlay_rect;
 
   damage_rect->Union(output_surface_overlay_damage_rect);

components/viz/service/display/overlay_unittest.cc

@@ -1893,6 +1893,39 @@ TEST_F(UnderlayTest, PrimaryPlaneOverlayIsTransparentWithUnderlay) {
   ASSERT_EQ(false, candidate_list[0].is_opaque);
 }
 
+TEST_F(UnderlayTest, UpdateDamageWhenChangingUnderlays) {
+  output_surface_->GetOverlayCandidateValidator()->AddExpectedRect(
+      gfx::RectF(kOverlayTopLeftRect));
+
+  for (size_t i = 0; i < 2; ++i) {
+    std::unique_ptr<RenderPass> pass = CreateRenderPass();
+
+    if (i == 0) {
+      CreateCandidateQuadAt(
+          resource_provider_.get(), child_resource_provider_.get(),
+          child_provider_.get(), pass->shared_quad_state_list.back(),
+          pass.get(), kOverlayRect);
+    }
+
+    CreateCandidateQuadAt(resource_provider_.get(),
+                          child_resource_provider_.get(), child_provider_.get(),
+                          pass->shared_quad_state_list.back(), pass.get(),
+                          kOverlayTopLeftRect);
+
+    OverlayCandidateList candidate_list;
+    OverlayProcessor::FilterOperationsMap render_pass_filters;
+    OverlayProcessor::FilterOperationsMap render_pass_background_filters;
+    RenderPassList pass_list;
+    pass_list.push_back(std::move(pass));
+    overlay_processor_->ProcessForOverlays(
+        resource_provider_.get(), &pass_list, GetIdentityColorMatrix(),
+        render_pass_filters, render_pass_background_filters, &candidate_list,
+        nullptr, nullptr, &damage_rect_, &content_bounds_);
+  }
+
+  EXPECT_EQ(kOverlayRect, damage_rect_);
+}
+
 TEST_F(UnderlayCastTest, NoOverlayContentBounds) {
   std::unique_ptr<RenderPass> pass = CreateRenderPass();