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 5b95f561685fa48533c61b4a1efebb5c894ae3e0..7655b0da5a4f1e52a3d48d6a566e964e72e2f133 100644
--- a/cc/animation/scroll_offset_animation_curve.cc
+++ b/cc/animation/scroll_offset_animation_curve.cc
@@ -114,17 +114,25 @@ void ScrollOffsetAnimationCurve::ApplyAdjustment(
   target_value_ = ScrollOffsetWithDelta(target_value_, adjustment);
 }
 
+void ScrollOffsetAnimationCurve::AdjustDuration(base::TimeDelta adjustment) {
+  base::TimeDelta old_duration = total_animation_duration_ - last_retarget_;
+  base::TimeDelta new_duration = old_duration - adjustment;
+  if (new_duration <= base::TimeDelta())
+    new_duration = base::TimeDelta();
+  total_animation_duration_ -= old_duration - new_duration;
+}
+
 gfx::ScrollOffset ScrollOffsetAnimationCurve::GetValue(
     base::TimeDelta t) const {
   base::TimeDelta duration = total_animation_duration_ - last_retarget_;
   t -= last_retarget_;
 
-  if (t <= base::TimeDelta())
-    return initial_value_;
-
   if (t >= duration)
     return target_value_;
 
+  if (t <= base::TimeDelta())
+    return initial_value_;
+
   double progress = timing_function_->GetValue(TimeUtil::Divide(t, duration));
   return gfx::ScrollOffset(
       gfx::Tween::FloatValueBetween(