Avoid rendering using GL in case damage rect is composited by overlay

We can avoid drawing using GL if the damage rect is entirely
composited by using overlays.

BUG=370522
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Committed: https://crrev.com/7c024b25d977484b627b63bff9f85e5b5e382b9e
Cr-Commit-Position: refs/heads/master@{#356844}

Review URL: https://codereview.chromium.org/1413763013

Cr-Commit-Position: refs/heads/master@{#359332}

2 files changed, 48 insertions, 0 deletions

diff --git a/cc/output/direct_renderer.cc b/cc/output/direct_renderer.cc
index 0a66eea..43e19c3 100644
--- a/cc/output/direct_renderer.cc
+++ b/cc/output/direct_renderer.cc
@@ -242,6 +242,25 @@ void DirectRenderer::DrawFrame(RenderPassList* render_passes_in_draw_order,
     overlay_processor_->ProcessForOverlays(
         resource_provider_, render_passes_in_draw_order, &frame.overlay_list,
         &frame.root_damage_rect);
+
+    // No need to render in case the damage rect is completely composited using
+    // overlays and dont have any copy requests.
+    if (frame.root_damage_rect.IsEmpty()) {
+      bool handle_copy_requests = false;
+      for (auto* pass : *render_passes_in_draw_order) {
+        if (!pass->copy_requests.empty()) {
+          handle_copy_requests = true;
+          break;
+        }
+      }
+
+      if (!handle_copy_requests) {
+        BindFramebufferToOutputSurface(&frame);
+        FinishDrawingFrame(&frame);
+        render_passes_in_draw_order->clear();
+        return;
+      }
+    }
   }
 
   for (size_t i = 0; i < render_passes_in_draw_order->size(); ++i) {
diff --git a/cc/output/overlay_unittest.cc b/cc/output/overlay_unittest.cc
index 8c9efc7..dd325bd 100644
--- a/cc/output/overlay_unittest.cc
+++ b/cc/output/overlay_unittest.cc
@@ -1613,6 +1613,35 @@ TEST_F(GLRendererWithOverlaysTest, NoValidatorNoOverlay) {
   Mock::VerifyAndClearExpectations(&scheduler_);
 }
 
+TEST_F(GLRendererWithOverlaysTest, OccludedQuadNotDrawn) {
+  bool use_validator = true;
+  Init(use_validator);
+  renderer_->set_expect_overlays(true);
+  gfx::Rect viewport_rect(16, 16);
+
+  scoped_ptr<RenderPass> pass = CreateRenderPass();
+
+  CreateFullscreenCandidateQuad(resource_provider_.get(),
+                                pass->shared_quad_state_list.back(),
+                                pass.get());
+
+  CreateFullscreenOpaqueQuad(resource_provider_.get(),
+                             pass->shared_quad_state_list.back(), pass.get());
+  CreateFullscreenOpaqueQuad(resource_provider_.get(),
+                             pass->shared_quad_state_list.back(), pass.get());
+
+  RenderPassList pass_list;
+  pass_list.push_back(pass.Pass());
+
+  output_surface_->set_is_displayed_as_overlay_plane(true);
+  EXPECT_CALL(*renderer_, DoDrawQuad(_, _, _)).Times(0);
+  EXPECT_CALL(scheduler_, Schedule(_, _, _, _, _)).Times(2);
+  renderer_->DrawFrame(&pass_list, 1.f, viewport_rect, viewport_rect, false);
+  SwapBuffers();
+  Mock::VerifyAndClearExpectations(renderer_.get());
+  Mock::VerifyAndClearExpectations(&scheduler_);
+}
+
 TEST_F(GLRendererWithOverlaysTest, ResourcesExportedAndReturnedWithDelay) {
   bool use_validator = true;
   Init(use_validator);