Scroll with Layers in views::ScrollView

cc/trees/layer_tree_host_impl.cc

 // Copyright 2011 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/trees/layer_tree_host_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 609 matching lines @@
 
 ScrollElasticityHelper* LayerTreeHostImpl::CreateScrollElasticityHelper() {
   DCHECK(!scroll_elasticity_helper_);
   if (settings_.enable_elastic_overscroll) {
     scroll_elasticity_helper_.reset(
         ScrollElasticityHelper::CreateForLayerTreeHostImpl(this));
   }
   return scroll_elasticity_helper_.get();
 }
 
+bool LayerTreeHostImpl::GetScrollOffsetForLayer(int layer_id,
+                                                gfx::ScrollOffset* offset) {
+  LayerImpl* layer = active_tree()->FindActiveTreeLayerById(layer_id);
+  if (!layer)
+    return false;
+
+  *offset = layer->CurrentScrollOffset();
+  return true;
+}
+
+bool LayerTreeHostImpl::ScrollLayerTo(int layer_id,
+                                      const gfx::ScrollOffset& offset) {
+  LayerImpl* layer = active_tree()->FindActiveTreeLayerById(layer_id);
+  if (!layer)
+    return false;
+
+  layer->ScrollBy(
+      ScrollOffsetToVector2dF(offset - layer->CurrentScrollOffset()));
+  return true;
+}
+
 void LayerTreeHostImpl::QueueSwapPromiseForMainThreadScrollUpdate(
     std::unique_ptr<SwapPromise> swap_promise) {
   swap_promises_for_main_thread_scroll_update_.push_back(
       std::move(swap_promise));
 }
 
 void LayerTreeHostImpl::TrackDamageForAllSurfaces(
     const LayerImplList& render_surface_layer_list) {
   // For now, we use damage tracking to compute a global scissor. To do this, we
   // must compute all damage tracking before drawing anything, so that we know
@@ skipping 3368 matching lines @@
   return task_runner_provider_->HasImplThread();
 }
 
 bool LayerTreeHostImpl::CommitToActiveTree() const {
   // In single threaded mode we skip the pending tree and commit directly to the
   // active tree.
   return !task_runner_provider_->HasImplThread();
 }
 
 }  // namespace cc