Communicate MT changes to impl-only scroll offset animations

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 04614b572c89e40df4844e7c648beff0a0130d80..a049554a22140f32c807bcd01d1d7a605722a8ec 100644
--- a/cc/animation/scroll_offset_animation_curve.cc
+++ b/cc/animation/scroll_offset_animation_curve.cc
@@ -108,6 +108,13 @@ bool ScrollOffsetAnimationCurve::HasSetInitialValue() const {
   return has_set_initial_value_;
 }
 
+void ScrollOffsetAnimationCurve::ApplyAdjustment(
+    base::TimeDelta t,
+    const gfx::Vector2dF& adjustment) {
+  SetInitialValue(ScrollOffsetWithDelta(GetValue(t), adjustment));
+  target_value_ = ScrollOffsetWithDelta(target_value_, adjustment);
+}
+
 gfx::ScrollOffset ScrollOffsetAnimationCurve::GetValue(
     base::TimeDelta t) const {
   base::TimeDelta duration = total_animation_duration_ - last_retarget_;