[BGPT] Allow direct transform/opacity update on the end of animation

We chose to skip direct transform/opacity if the property is animating
in compositor in crrev.com/c/1565467 (fast-path for simple transform
change) to reduce risk of it.

We observed that it caused regressions for several benchmarks. Now
allow direct transform/opacity on the end of animation in this separate
CL.

We already have several test cases testing the situation.

Bug: 954611
Change-Id: I6a8516dba92f6a3b02efd664bbc12315fe94d63b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1585263Reviewed-by: Philip Rogers <pdr@chromium.org>
Reviewed-by: vmpstr <vmpstr@chromium.org>
Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#654497}

third_party/blink/renderer/platform/graphics/compositing/property_tree_manager.cc

@@ -85,9 +85,14 @@ bool PropertyTreeManager::DirectlyUpdateCompositedOpacityValue(
   if (it == effect_node_map_.end())
     return false;
   auto* cc_effect = property_trees->effect_tree.Node(it->value);
-  if (!cc_effect || cc_effect->is_currently_animating_opacity)
+  if (!cc_effect)
     return false;
 
+  // We directly update opacity only when it's not animating in compositor. If
+  // the compositor has not cleared is_currently_animating_opacity, we should
+  // clear it now to let the compositor respect the new value.
+  cc_effect->is_currently_animating_opacity = false;
+
   cc_effect->opacity = effect.Opacity();
   cc_effect->effect_changed = true;
   property_trees->effect_tree.set_needs_update(true);
@@ -112,9 +117,11 @@ bool PropertyTreeManager::DirectlyUpdateScrollOffsetTransform(
     return false;
   auto* cc_transform = property_trees->transform_tree.Node(transform_it->value);
 
-  if (!cc_scroll_node || !cc_transform || cc_transform->is_currently_animating)
+  if (!cc_scroll_node || !cc_transform)
     return false;
 
+  DCHECK(!cc_transform->is_currently_animating);
+
   UpdateCcTransformLocalMatrix(*cc_transform, transform);
   SetCcTransformNodeScrollToTransformTranslation(*cc_transform, transform);
   property_trees->scroll_tree.SetScrollOffset(
@@ -137,11 +144,16 @@ bool PropertyTreeManager::DirectlyUpdateTransform(
   if (transform_it == transform_node_map_.end())
     return false;
   auto* cc_transform = property_trees->transform_tree.Node(transform_it->value);
-  if (!cc_transform || cc_transform->is_currently_animating)
+  if (!cc_transform)
     return false;
 
   UpdateCcTransformLocalMatrix(*cc_transform, transform);
 
+  // We directly update transform only when the transform is not animating in
+  // compositor. If the compositor has not cleared the is_currently_animating
+  // flag, we should clear it to let the compositor respect the new value.
+  cc_transform->is_currently_animating = false;
+
   cc_transform->transform_changed = true;
   property_trees->transform_tree.set_needs_update(true);
   return true;