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

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index f1ef243b83c595dcbfda11fe6afb26488f1a3c20..83a67283fd820257702c693cdbe1bef1a87b0a1c 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -2778,8 +2778,10 @@ gfx::Vector2dF LayerTreeHostImpl::ComputeScrollDelta(
   return gfx::Vector2dF(scrolled.x(), scrolled.y());
 }
 
-bool LayerTreeHostImpl::ScrollAnimationCreate(ScrollNode* scroll_node,
-                                              const gfx::Vector2dF& delta) {
+bool LayerTreeHostImpl::ScrollAnimationCreate(
+    ScrollNode* scroll_node,
+    const gfx::Vector2dF& delta,
+    base::TimeTicks original_event_time) {
   ScrollTree& scroll_tree = active_tree_->property_trees()->scroll_tree;
 
   const float kEpsilon = 0.1f;
@@ -2797,7 +2799,8 @@ bool LayerTreeHostImpl::ScrollAnimationCreate(ScrollNode* scroll_node,
   gfx::ScrollOffset target_offset = scroll_tree.ClampScrollOffsetToLimits(
       current_offset + gfx::ScrollOffset(delta), scroll_node);
   animation_host_->ImplOnlyScrollAnimationCreate(scroll_node->owner_id,
-                                                 target_offset, current_offset);
+                                                 target_offset, current_offset,
+                                                 original_event_time);
 
   SetNeedsOneBeginImplFrame();
 
@@ -2806,7 +2809,8 @@ bool LayerTreeHostImpl::ScrollAnimationCreate(ScrollNode* scroll_node,
 
 InputHandler::ScrollStatus LayerTreeHostImpl::ScrollAnimated(
     const gfx::Point& viewport_point,
-    const gfx::Vector2dF& scroll_delta) {
+    const gfx::Vector2dF& scroll_delta,
+    const ui::LatencyInfo* latency_info) {
   InputHandler::ScrollStatus scroll_status;
   scroll_status.main_thread_scrolling_reasons =
       MainThreadScrollingReason::kNotScrollingOnMain;
@@ -2850,8 +2854,18 @@ InputHandler::ScrollStatus LayerTreeHostImpl::ScrollAnimated(
             scroll_node->data.is_outer_viewport_scroll_layer)
           continue;
 
+        // Some time may have passed between now and when the user actually
+        // asked to scroll. The animation curve should take this into account
+        // in the duration of the animation.
+        ui::LatencyInfo::LatencyComponent o_component;
+        o_component.event_time = base::TimeTicks();
+        if (latency_info)
+          latency_info->FindLatency(ui::INPUT_EVENT_LATENCY_ORIGINAL_COMPONENT,
+                                    0, &o_component);
+
         if (scroll_node->data.is_inner_viewport_scroll_layer) {
-          gfx::Vector2dF scrolled = viewport()->ScrollAnimated(pending_delta);
+          gfx::Vector2dF scrolled =
+              viewport()->ScrollAnimated(pending_delta, o_component.event_time);
           // Viewport::ScrollAnimated returns pending_delta as long as it
           // starts an animation.
           if (scrolled == pending_delta)
@@ -2862,7 +2876,8 @@ InputHandler::ScrollStatus LayerTreeHostImpl::ScrollAnimated(
 
         gfx::Vector2dF scroll_delta =
             ComputeScrollDelta(scroll_node, pending_delta);
-        if (ScrollAnimationCreate(scroll_node, scroll_delta))
+        if (ScrollAnimationCreate(scroll_node, scroll_delta,
+                                  o_component.event_time))
           return scroll_status;
 
         pending_delta -= scroll_delta;