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 54f6fb70d8cb80941011638d0dcc0ff0ecd3909b..cb89f11a77ebd1815a629ce7d23e7e772eac5ef2 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_;