Communicate MT changes to impl-only scroll offset animations

cc/animation/scroll_offset_animation_curve.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/animation/scroll_offset_animation_curve.h"
 
 #include <algorithm>
 #include <cmath>
 
 #include "base/logging.h"
@@ skipping 90 matching lines @@
   initial_value_ = initial_value;
   has_set_initial_value_ = true;
   total_animation_duration_ = SegmentDuration(
       target_value_.DeltaFrom(initial_value_), duration_behavior_);
 }
 
 bool ScrollOffsetAnimationCurve::HasSetInitialValue() const {
   return has_set_initial_value_;
 }
 
+void ScrollOffsetAnimationCurve::ApplyAdjustment(
+    const gfx::Vector2dF& adjustment) {
+  initial_value_ = ScrollOffsetWithDelta(initial_value_, adjustment);
+  target_value_ = ScrollOffsetWithDelta(target_value_, adjustment);
+}
+
 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_;
@@ skipping 99 matching lines @@
       (MaximumDimension(old_delta) / MaximumDimension(new_delta));
 
   initial_value_ = current_position;
   target_value_ = new_target;
   total_animation_duration_ = base::TimeDelta::FromSecondsD(t + new_duration);
   last_retarget_ = base::TimeDelta::FromSecondsD(t);
   timing_function_ = EaseOutWithInitialVelocity(new_normalized_velocity);
 }
 
 }  // namespace cc