Take MT jank into account when animating the scroll offset on CC

cc/animation/scroll_offset_animation_curve.cc

Index: cc/animation/scroll_offset_animation_curve.cc
diff --git a/cc/animation/scroll_offset_animation_curve.cc b/cc/animation/scroll_offset_animation_curve.cc
index b207994c092a327a70c753d99b7c93f4446bf4c2..d5dd4d5959c7d27a6b4b742a3e9690b46e498886 100644
--- a/cc/animation/scroll_offset_animation_curve.cc
+++ b/cc/animation/scroll_offset_animation_curve.cc
@@ -41,7 +41,8 @@ static float MaximumDimension(const gfx::Vector2dF& delta) {
 }
 
 static base::TimeDelta SegmentDuration(const gfx::Vector2dF& delta,
-                                       DurationBehavior behavior) {
+                                       DurationBehavior behavior,
+                                       base::TimeDelta delayed_by) {
   double duration = kConstantDuration;
   switch (behavior) {
     case DurationBehavior::CONSTANT:
@@ -60,8 +61,14 @@ static base::TimeDelta SegmentDuration(const gfx::Vector2dF& delta,
     default:
       NOTREACHED();
   }
-  return base::TimeDelta::FromMicroseconds(duration / kDurationDivisor *
-                                           base::Time::kMicrosecondsPerSecond);
+
+  base::TimeDelta time_delta = base::TimeDelta::FromMicroseconds(
+      duration / kDurationDivisor * base::Time::kMicrosecondsPerSecond);
+
+  time_delta -= delayed_by;
+  if (time_delta >= base::TimeDelta())
+    return time_delta;
+  return base::TimeDelta();
 }
 
 static std::unique_ptr<TimingFunction> EaseOutWithInitialVelocity(
@@ -98,11 +105,12 @@ ScrollOffsetAnimationCurve::ScrollOffsetAnimationCurve(
 ScrollOffsetAnimationCurve::~ScrollOffsetAnimationCurve() {}
 
 void ScrollOffsetAnimationCurve::SetInitialValue(
-    const gfx::ScrollOffset& initial_value) {
+    const gfx::ScrollOffset& initial_value,
+    base::TimeDelta delayed_by) {
   initial_value_ = initial_value;
   has_set_initial_value_ = true;
   total_animation_duration_ = SegmentDuration(
-      target_value_.DeltaFrom(initial_value_), duration_behavior_);
+      target_value_.DeltaFrom(initial_value_), duration_behavior_, delayed_by);
 }
 
 bool ScrollOffsetAnimationCurve::HasSetInitialValue() const {
@@ -120,6 +128,9 @@ gfx::ScrollOffset ScrollOffsetAnimationCurve::GetValue(
   base::TimeDelta duration = total_animation_duration_ - last_retarget_;
   t -= last_retarget_;
 
+  if (duration.is_zero())
+    return target_value_;
+
   if (t <= base::TimeDelta())
     return initial_value_;
 
@@ -190,10 +201,13 @@ void ScrollOffsetAnimationCurve::UpdateTarget(
     double t,
     const gfx::ScrollOffset& new_target) {
   if (std::abs(MaximumDimension(target_value_.DeltaFrom(new_target))) <
-      kEpsilon) {
+          kEpsilon ||
+      total_animation_duration_.is_zero()) {
     target_value_ = new_target;
     return;
   }
+
+  t = std::max(t, last_retarget_.InSecondsF());
   gfx::ScrollOffset current_position =
       GetValue(base::TimeDelta::FromSecondsD(t));
   gfx::Vector2dF old_delta = target_value_.DeltaFrom(initial_value_);
@@ -208,7 +222,8 @@ void ScrollOffsetAnimationCurve::UpdateTarget(
   // segment duration. This minimizes the "rubber-band" bouncing effect when
   // old_normalized_velocity is large and new_delta is small.
   double new_duration =
-      std::min(SegmentDuration(new_delta, duration_behavior_).InSecondsF(),
+      std::min(SegmentDuration(new_delta, duration_behavior_, base::TimeDelta())
+                   .InSecondsF(),
                VelocityBasedDurationBound(old_delta, old_normalized_velocity,
                                           old_duration, new_delta));