cc: Ignore certain quads that would otherwise block overlays

If a quad is fully transparent then it shouldn't block overlays. For
now we allow some SOLID_COLOR quads through

Review URL: https://codereview.chromium.org/880023005

Cr-Commit-Position: refs/heads/master@{#315106}

cc/output/overlay_strategy_single_on_top.cc

@@ -119,6 +119,20 @@ bool OverlayStrategySingleOnTop::GetCandidateQuadInfo(
   return true;
 }
 
+bool OverlayStrategySingleOnTop::IsInvisibleQuad(const DrawQuad* draw_quad) {
+  if (draw_quad->material == DrawQuad::SOLID_COLOR) {
+    const SolidColorDrawQuad* solid_quad =
+        SolidColorDrawQuad::MaterialCast(draw_quad);
+    SkColor color = solid_quad->color;
+    float opacity = solid_quad->opacity();
+    float alpha = (SkColorGetA(color) * (1.0f / 255.0f)) * opacity;
+    // Ignore transparent solid color quads.
+    return solid_quad->ShouldDrawWithBlending() &&
+           alpha < std::numeric_limits<float>::epsilon();
+  }
+  return false;
+}
+
 bool OverlayStrategySingleOnTop::Attempt(
     RenderPassList* render_passes_in_draw_order,
     OverlayCandidateList* candidate_list) {
@@ -143,7 +157,7 @@ bool OverlayStrategySingleOnTop::Attempt(
            ++overlap_iter) {
         gfx::RectF overlap_rect = overlap_iter->rect;
         overlap_iter->quadTransform().TransformRect(&overlap_rect);
-        if (rect.Intersects(overlap_rect)) {
+        if (rect.Intersects(overlap_rect) && !IsInvisibleQuad(*overlap_iter)) {
           intersects = true;
           break;
         }

cc/output/overlay_strategy_single_on_top.h

@@ -29,6 +29,10 @@ class CC_EXPORT OverlayStrategySingleOnTop : public OverlayProcessor::Strategy {
   bool GetCandidateQuadInfo(const DrawQuad& draw_quad,
                             OverlayCandidate* quad_info);
 
+  // Returns true if |draw_quad| will not block quads underneath from becoming
+  // an overlay.
+  bool IsInvisibleQuad(const DrawQuad* draw_quad);
+
   bool GetTextureQuadInfo(const TextureDrawQuad& quad,
                           OverlayCandidate* quad_info);
   bool GetVideoQuadInfo(const StreamVideoDrawQuad& quad,

cc/output/overlay_unittest.cc

@@ -156,6 +156,17 @@ ResourceProvider::ResourceId CreateResource(
       mailbox, release_callback.Pass());
 }
 
+SolidColorDrawQuad* CreateSolidColorQuadAt(
+    const SharedQuadState* shared_quad_state,
+    SkColor color,
+    RenderPass* render_pass,
+    const gfx::Rect& rect) {
+  SolidColorDrawQuad* quad =
+      render_pass->CreateAndAppendDrawQuad<SolidColorDrawQuad>();
+  quad->SetNew(shared_quad_state, rect, rect, color, false);
+  return quad;
+}
+
 TextureDrawQuad* CreateCandidateQuadAt(ResourceProvider* resource_provider,
                                        const SharedQuadState* shared_quad_state,
                                        RenderPass* render_pass,
@@ -592,6 +603,94 @@ TEST_F(SingleOverlayOnTopTest, AllowNotTopIfNotOccluded) {
   EXPECT_EQ(2U, candidate_list.size());
 }
 
+TEST_F(SingleOverlayOnTopTest, AllowTransparentOnTop) {
+  scoped_ptr<RenderPass> pass = CreateRenderPass();
+  SharedQuadState* shared_state = pass->CreateAndAppendSharedQuadState();
+  shared_state->opacity = 0.f;
+  CreateSolidColorQuadAt(shared_state, SK_ColorBLACK, pass.get(),
+                         kOverlayBottomRightRect);
+  shared_state = pass->CreateAndAppendSharedQuadState();
+  shared_state->opacity = 1.f;
+  CreateCandidateQuadAt(resource_provider_.get(), shared_state, pass.get(),
+                        kOverlayBottomRightRect);
+
+  RenderPassList pass_list;
+  pass_list.push_back(pass.Pass());
+
+  RenderPassList original_pass_list;
+  RenderPass::CopyAll(pass_list, &original_pass_list);
+
+  OverlayCandidateList candidate_list;
+  overlay_processor_->ProcessForOverlays(&pass_list, &candidate_list);
+  EXPECT_EQ(1U, pass_list.size());
+  EXPECT_EQ(2U, candidate_list.size());
+}
+
+TEST_F(SingleOverlayOnTopTest, AllowTransparentColorOnTop) {
+  scoped_ptr<RenderPass> pass = CreateRenderPass();
+  CreateSolidColorQuadAt(pass->shared_quad_state_list.back(),
+                         SK_ColorTRANSPARENT, pass.get(),
+                         kOverlayBottomRightRect);
+  CreateCandidateQuadAt(resource_provider_.get(),
+                        pass->shared_quad_state_list.back(), pass.get(),
+                        kOverlayBottomRightRect);
+
+  RenderPassList pass_list;
+  pass_list.push_back(pass.Pass());
+
+  RenderPassList original_pass_list;
+  RenderPass::CopyAll(pass_list, &original_pass_list);
+
+  OverlayCandidateList candidate_list;
+  overlay_processor_->ProcessForOverlays(&pass_list, &candidate_list);
+  EXPECT_EQ(1U, pass_list.size());
+  EXPECT_EQ(2U, candidate_list.size());
+}
+
+TEST_F(SingleOverlayOnTopTest, RejectOpaqueColorOnTop) {
+  scoped_ptr<RenderPass> pass = CreateRenderPass();
+  SharedQuadState* shared_state = pass->CreateAndAppendSharedQuadState();
+  shared_state->opacity = 0.5f;
+  CreateSolidColorQuadAt(shared_state, SK_ColorBLACK, pass.get(),
+                         kOverlayBottomRightRect);
+  shared_state = pass->CreateAndAppendSharedQuadState();
+  shared_state->opacity = 1.f;
+  CreateCandidateQuadAt(resource_provider_.get(), shared_state, pass.get(),
+                        kOverlayBottomRightRect);
+
+  RenderPassList pass_list;
+  pass_list.push_back(pass.Pass());
+
+  RenderPassList original_pass_list;
+  RenderPass::CopyAll(pass_list, &original_pass_list);
+
+  OverlayCandidateList candidate_list;
+  overlay_processor_->ProcessForOverlays(&pass_list, &candidate_list);
+  EXPECT_EQ(1U, pass_list.size());
+  EXPECT_EQ(0U, candidate_list.size());
+}
+
+TEST_F(SingleOverlayOnTopTest, RejectTransparentColorOnTopWithoutBlending) {
+  scoped_ptr<RenderPass> pass = CreateRenderPass();
+  SharedQuadState* shared_state = pass->CreateAndAppendSharedQuadState();
+  CreateSolidColorQuadAt(shared_state, SK_ColorTRANSPARENT, pass.get(),
+                         kOverlayBottomRightRect)->opaque_rect =
+      kOverlayBottomRightRect;
+  CreateCandidateQuadAt(resource_provider_.get(), shared_state, pass.get(),
+                        kOverlayBottomRightRect);
+
+  RenderPassList pass_list;
+  pass_list.push_back(pass.Pass());
+
+  RenderPassList original_pass_list;
+  RenderPass::CopyAll(pass_list, &original_pass_list);
+
+  OverlayCandidateList candidate_list;
+  overlay_processor_->ProcessForOverlays(&pass_list, &candidate_list);
+  EXPECT_EQ(1U, pass_list.size());
+  EXPECT_EQ(0U, candidate_list.size());
+}
+
 TEST_F(SingleOverlayOnTopTest, RejectVideoSwapTransform) {
   scoped_ptr<RenderPass> pass = CreateRenderPass();
   CreateFullscreenCandidateVideoQuad(resource_provider_.get(),