Reset the state of the previous frame if hardware overlay processing is skipped.

If hardware overlay processing is skipped for a frame, there's no
way to be sure of the state of the previous frame. Reset
|previous_frame_underlay_rect_| for the next frame.

BUG=Internal b/37644269
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel

Review-Url: https://codereview.chromium.org/2844483004
Cr-Commit-Position: refs/heads/master@{#467754}

cc/output/overlay_processor.cc

@@ -128,14 +128,16 @@ void OverlayProcessor::ProcessForOverlays(
   SendPromotionHintsBeforeReturning notifier(resource_provider, candidates);
 #endif
 
+  // Reset |previous_frame_underlay_rect_| in case UpdateDamageRect() not being
+  // invoked.
+  const gfx::Rect previous_frame_underlay_rect = previous_frame_underlay_rect_;
+  previous_frame_underlay_rect_ = gfx::Rect();
+
   // If we have any copy requests, we can't remove any quads for overlays or
   // CALayers because the framebuffer would be missing the removed quads'
   // contents.
   if (!render_pass->copy_requests.empty()) {
     dc_processor_.ClearOverlayState();
-    // If overlay processing was skipped for a frame there's no way to be sure
-    // of the state of the previous frame, so reset.
-    previous_frame_underlay_rect_ = gfx::Rect();
     return;
   }
 
@@ -158,7 +160,7 @@ void OverlayProcessor::ProcessForOverlays(
                            content_bounds))
       continue;
 
-    UpdateDamageRect(candidates, damage_rect);
+    UpdateDamageRect(candidates, previous_frame_underlay_rect, damage_rect);
     return;
   }
 }
@@ -171,8 +173,10 @@ void OverlayProcessor::ProcessForOverlays(
 // 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.
-void OverlayProcessor::UpdateDamageRect(OverlayCandidateList* candidates,
-                                        gfx::Rect* damage_rect) {
+void OverlayProcessor::UpdateDamageRect(
+    OverlayCandidateList* candidates,
+    const gfx::Rect& previous_frame_underlay_rect,
+    gfx::Rect* damage_rect) {
   gfx::Rect output_surface_overlay_damage_rect;
   gfx::Rect this_frame_underlay_rect;
   for (const OverlayCandidate& overlay : *candidates) {
@@ -189,7 +193,7 @@ void OverlayProcessor::UpdateDamageRect(OverlayCandidateList* candidates,
     }
   }
 
-  if (this_frame_underlay_rect == previous_frame_underlay_rect_)
+  if (this_frame_underlay_rect == previous_frame_underlay_rect)
     damage_rect->Subtract(this_frame_underlay_rect);
   previous_frame_underlay_rect_ = this_frame_underlay_rect;
 

cc/output/overlay_processor.h

@@ -83,6 +83,7 @@ class CC_EXPORT OverlayProcessor {
       gfx::Rect* damage_rect);
   // Update |damage_rect| by removing damage casued by |candidates|.
   void UpdateDamageRect(OverlayCandidateList* candidates,
+                        const gfx::Rect& previous_frame_underlay_rect,
                         gfx::Rect* damage_rect);
 
   DCLayerOverlayProcessor dc_processor_;

cc/output/overlay_unittest.cc

@@ -1400,6 +1400,38 @@ TEST_F(UnderlayTest, DamageNotSubtractedForNonIdenticalConsecutiveUnderlays) {
   }
 }
 
+// Underlay damage can only be subtracted if the previous frame's underlay
+// exists.
+TEST_F(UnderlayTest, DamageNotSubtractedForNonConsecutiveIdenticalUnderlays) {
+  bool has_fullscreen_candidate[] = {true, false, true};
+
+  for (int i = 0; i < 3; ++i) {
+    std::unique_ptr<RenderPass> pass = CreateRenderPass();
+
+    if (has_fullscreen_candidate[i]) {
+      CreateFullscreenCandidateQuad(resource_provider_.get(),
+                                    pass->shared_quad_state_list.back(),
+                                    pass.get());
+    }
+
+    damage_rect_ = kOverlayRect;
+
+    // Add something behind it.
+    CreateFullscreenOpaqueQuad(resource_provider_.get(),
+                               pass->shared_quad_state_list.back(), pass.get());
+
+    OverlayCandidateList candidate_list;
+    base::flat_map<int, FilterOperations*> render_pass_filters;
+    base::flat_map<int, FilterOperations*> render_pass_background_filters;
+    overlay_processor_->ProcessForOverlays(
+        resource_provider_.get(), pass.get(), render_pass_filters,
+        render_pass_background_filters, &candidate_list, nullptr, nullptr,
+        &damage_rect_, &content_bounds_);
+  }
+
+  EXPECT_EQ(kOverlayRect, damage_rect_);
+}
+
 TEST_F(UnderlayTest, DamageNotSubtractedWhenQuadsAboveOverlap) {
   for (int i = 0; i < 2; ++i) {
     std::unique_ptr<RenderPass> pass = CreateRenderPass();