cc: Impl thread scroll on ScrollNode instead of LayerImpl

cc/layers/layer_impl.cc

Index: cc/layers/layer_impl.cc
diff --git a/cc/layers/layer_impl.cc b/cc/layers/layer_impl.cc
index 6cdc4234b68b3099a485fda32f3511fa46ee71cc..2221f6b2e83e06f22f53f06190a3c90a90f10c76 100644
--- a/cc/layers/layer_impl.cc
+++ b/cc/layers/layer_impl.cc
@@ -207,7 +207,9 @@ void LayerImpl::DistributeScroll(ScrollState* scroll_state) {
 
 void LayerImpl::ApplyScroll(ScrollState* scroll_state) {
   DCHECK(scroll_state);
-  layer_tree_impl()->ApplyScroll(this, scroll_state);
+  ScrollNode* node = layer_tree_impl()->property_trees()->scroll_tree.Node(
+      scroll_tree_index());
+  layer_tree_impl()->ApplyScroll(node, scroll_state);
 }
 
 void LayerImpl::SetNumDescendantsThatDrawContent(int num_descendants) {
@@ -427,20 +429,9 @@ void LayerImpl::GetContentsResourceId(ResourceId* resource_id,
 }
 
 gfx::Vector2dF LayerImpl::ScrollBy(const gfx::Vector2dF& scroll) {
-  gfx::ScrollOffset adjusted_scroll(scroll);
-  if (!user_scrollable_horizontal_)
-    adjusted_scroll.set_x(0);
-  if (!user_scrollable_vertical_)
-    adjusted_scroll.set_y(0);
-  DCHECK(scrollable());
-  gfx::ScrollOffset old_offset = CurrentScrollOffset();
-  gfx::ScrollOffset new_offset =
-      ClampScrollOffsetToLimits(old_offset + adjusted_scroll);
-  SetCurrentScrollOffset(new_offset);
-
-  gfx::ScrollOffset unscrolled =
-      old_offset + gfx::ScrollOffset(scroll) - new_offset;
-  return gfx::Vector2dF(unscrolled.x(), unscrolled.y());
+  ScrollTree& scroll_tree = layer_tree_impl()->property_trees()->scroll_tree;
+  ScrollNode* scroll_node = scroll_tree.Node(scroll_tree_index());
+  return scroll_tree.ScrollBy(scroll_node, scroll, layer_tree_impl());
 }
 
 void LayerImpl::SetScrollClipLayer(int scroll_clip_layer_id) {
@@ -460,6 +451,24 @@ bool LayerImpl::scrollable() const {
   return scroll_clip_layer_id_ != Layer::INVALID_ID;
 }
 
+void LayerImpl::set_user_scrollable_horizontal(bool scrollable) {
+  user_scrollable_horizontal_ = scrollable;
+  if (!layer_tree_impl_->property_trees()->needs_rebuild && layer_tree_impl_ &&

[ajuma, 2016/03/16 21:49:24]

Horizontal/vertical scrollability should never change on the compositor thread
outside of tests, so rather than trying to update the scroll tree here, tests
that want to change this should just rebuild property trees.

[sunxd, 2016/03/16 23:30:23]

Done.

+      scroll_tree_index_ != -1)
+    layer_tree_impl_->property_trees()
+        ->scroll_tree.Node(scroll_tree_index_)
+        ->data.user_scrollable_horizontal = scrollable;
+}
+
+void LayerImpl::set_user_scrollable_vertical(bool scrollable) {
+  user_scrollable_vertical_ = scrollable;
+  if (!layer_tree_impl_->property_trees()->needs_rebuild && layer_tree_impl_ &&
+      scroll_tree_index_ != -1)
+    layer_tree_impl_->property_trees()
+        ->scroll_tree.Node(scroll_tree_index_)
+        ->data.user_scrollable_vertical = scrollable;
+}
+
 bool LayerImpl::user_scrollable(ScrollbarOrientation orientation) const {
   return (orientation == HORIZONTAL) ? user_scrollable_horizontal_
                                      : user_scrollable_vertical_;