[scroll-animations] Make Scroll/DocumentTimeline decision earlier

Instead of storing a ScrollTimeline that may be nullptr, store an
AnimationTimeline that's already been determined to either be a
ScrollTimeline or a DocumentTimeline.

There should be no behavior change in this CL. It's a preparation that
will make subsequent work on dynamically updatable @scroll-timeline
rules a bit smoother.

It's also needed in the future to differentiate between animation-
timeline:auto and animation-timeline:none.

Note: Apparently inspector_css_cascade_test.cc previously depended on
some header transitively included via css_animation_update.h.

Bug: 1074052
Change-Id: Ic9704f3a08859244163fd911b65bef98bc0b2d74
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2332618Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Reviewed-by: Kevin Ellis <kevers@chromium.org>
Commit-Queue: Anders Hartvoll Ruud <andruud@chromium.org>
Cr-Commit-Position: refs/heads/master@{#795218}

third_party/blink/renderer/core/animation/css/css_animation_update.h

@@ -6,11 +6,11 @@
 #define THIRD_PARTY_BLINK_RENDERER_CORE_ANIMATION_CSS_CSS_ANIMATION_UPDATE_H_
 
 #include "base/macros.h"
+#include "third_party/blink/renderer/core/animation/animation_timeline.h"
 #include "third_party/blink/renderer/core/animation/effect_stack.h"
 #include "third_party/blink/renderer/core/animation/inert_effect.h"
 #include "third_party/blink/renderer/core/animation/interpolation.h"
 #include "third_party/blink/renderer/core/animation/keyframe_effect_model.h"
-#include "third_party/blink/renderer/core/animation/scroll_timeline.h"
 #include "third_party/blink/renderer/core/css/css_keyframes_rule.h"
 #include "third_party/blink/renderer/core/css/css_property_equality.h"
 #include "third_party/blink/renderer/platform/wtf/allocator/allocator.h"
@@ -33,7 +33,7 @@ class NewCSSAnimation {
                   const InertEffect& effect,
                   Timing timing,
                   StyleRuleKeyframes* style_rule,
-                  ScrollTimeline* scroll_timeline,
+                  AnimationTimeline* timeline,
                   const Vector<EAnimPlayState>& play_state_list)
       : name(name),
         name_index(name_index),
@@ -42,13 +42,13 @@ class NewCSSAnimation {
         timing(timing),
         style_rule(style_rule),
         style_rule_version(this->style_rule->Version()),
-        scroll_timeline(scroll_timeline),
+        timeline(timeline),
         play_state_list(play_state_list) {}
 
   void Trace(Visitor* visitor) const {
     visitor->Trace(effect);
     visitor->Trace(style_rule);
-    visitor->Trace(scroll_timeline);
+    visitor->Trace(timeline);
   }
 
   AtomicString name;
@@ -58,7 +58,7 @@ class NewCSSAnimation {
   Timing timing;
   Member<StyleRuleKeyframes> style_rule;
   unsigned style_rule_version;
-  Member<ScrollTimeline> scroll_timeline;
+  Member<AnimationTimeline> timeline;
   Vector<EAnimPlayState> play_state_list;
 };
 
@@ -121,11 +121,11 @@ class CORE_EXPORT CSSAnimationUpdate final {
                       const InertEffect& effect,
                       const Timing& timing,
                       StyleRuleKeyframes* style_rule,
-                      ScrollTimeline* scroll_timeline,
+                      AnimationTimeline* timeline,
                       const Vector<EAnimPlayState>& play_state_list) {
     new_animations_.push_back(
         NewCSSAnimation(animation_name, name_index, position_index, effect,
-                        timing, style_rule, scroll_timeline, play_state_list));
+                        timing, style_rule, timeline, play_state_list));
   }
   void CancelAnimation(wtf_size_t index, const Animation& animation) {
     cancelled_animation_indices_.push_back(index);

third_party/blink/renderer/core/animation/css/css_animations.cc

@@ -529,6 +529,15 @@ ScrollTimeline* CreateScrollTimeline(Element* element,
   return scroll_timeline;
 }
 
+AnimationTimeline* ComputeTimeline(Element* element,
+                                   StyleRuleScrollTimeline* rule) {
+  if (rule) {
+    if (auto* timeline = CreateScrollTimeline(element, rule))
+      return timeline;
+  }
+  return &element->GetDocument().Timeline();
+}
+
 }  // namespace
 
 CSSAnimations::CSSAnimations() = default;
@@ -675,19 +684,18 @@ void CSSAnimations::CalculateAnimationUpdate(CSSAnimationUpdate& update,
 
       const StyleNameOrKeyword& timeline_name = animation_data->GetTimeline(i);
 
-      ScrollTimeline* scroll_timeline = nullptr;
+      StyleRuleScrollTimeline* scroll_timeline_rule = nullptr;
 
       // TODO(crbug.com/1097046): Support 'none' keyword.
       if (!timeline_name.IsKeyword()) {
-        StyleRuleScrollTimeline* scroll_timeline_rule =
+        scroll_timeline_rule =
             element.GetDocument().GetStyleEngine().FindScrollTimelineRule(
                 timeline_name.GetName().GetValue());
-        if (scroll_timeline_rule) {
-          scroll_timeline =
-              CreateScrollTimeline(&element, scroll_timeline_rule);
-        }
       }
 
+      AnimationTimeline* timeline =
+          ComputeTimeline(&element, scroll_timeline_rule);
+
       const RunningAnimation* existing_animation = nullptr;
       wtf_size_t existing_animation_index = 0;
 
@@ -751,9 +759,9 @@ void CSSAnimations::CalculateAnimationUpdate(CSSAnimationUpdate& update,
         DCHECK(!is_animation_style_change);
         base::Optional<TimelinePhase> inherited_phase;
         base::Optional<double> inherited_time = 0;
-        if (scroll_timeline) {
-          inherited_phase = base::make_optional(scroll_timeline->Phase());
-          inherited_time = scroll_timeline->CurrentTimeSeconds();
+        if (timeline && timeline->IsScrollTimeline()) {
+          inherited_phase = base::make_optional(timeline->Phase());
+          inherited_time = timeline->CurrentTimeSeconds();
         }
         update.StartAnimation(
             name, name_index, i,
@@ -762,7 +770,7 @@ void CSSAnimations::CalculateAnimationUpdate(CSSAnimationUpdate& update,
                                           &style, parent_style, name,
                                           keyframe_timing_function.get(), i),
                 timing, is_paused, inherited_time, inherited_phase),
-            specified_timing, keyframes_rule, scroll_timeline,
+            specified_timing, keyframes_rule, timeline,
             animation_data->PlayStateList());
       }
     }
@@ -903,9 +911,11 @@ void CSSAnimations::MaybeApplyPendingUpdate(Element* element) {
         element, inert_animation->Model(), inert_animation->SpecifiedTiming(),
         KeyframeEffect::kDefaultPriority, event_delegate);
 
-    AnimationTimeline* timeline = &element->GetDocument().Timeline();
-    if (entry.scroll_timeline)
-      timeline = entry.scroll_timeline.Get();
+    AnimationTimeline* timeline = entry.timeline;
+    // We always fall back to the DocumentTimeline at the moment, so the
+    // timeline can't be nullptr here.
+    // TODO(crbug.com/1097046): Support animation-timeline:none
+    DCHECK(timeline);
     auto* animation = MakeGarbageCollected<CSSAnimation>(
         element->GetExecutionContext(), timeline, effect, entry.position_index,
         entry.name);

third_party/blink/renderer/core/inspector/inspector_css_cascade_test.cc

@@ -6,6 +6,7 @@
 
 #include "testing/gtest/include/gtest/gtest.h"
 #include "third_party/blink/renderer/core/css/css_value.h"
+#include "third_party/blink/renderer/core/css/css_value_list.h"
 #include "third_party/blink/renderer/core/css/style_engine.h"
 #include "third_party/blink/renderer/core/html/html_element.h"
 #include "third_party/blink/renderer/core/style/computed_style_constants.h"