[not for review - epic CL] Adding Elastic+Momentum+Layered scrolling to views::ScrollView

ui/compositor/layer.cc

Index: ui/compositor/layer.cc
diff --git a/ui/compositor/layer.cc b/ui/compositor/layer.cc
index 7dcf17724f2ca838e763b2198a5a347d6f13a22a..dd02128d0ff9cc9ae4d44dd4b503135d4ca79041 100644
--- a/ui/compositor/layer.cc
+++ b/ui/compositor/layer.cc
@@ -528,6 +528,36 @@ void Layer::SwitchCCLayerForTest() {
   content_layer_ = new_layer;
 }
 
+gfx::ScrollOffset Layer::CurrentScrollOffset() const {
+  const Compositor* compositor = GetCompositor();
+  if (compositor)
+    return compositor->GetScrollOffsetForLayer(cc_layer_->id());
+  return cc_layer_->scroll_offset();
+}
+
+void Layer::SetScrollOffset(const gfx::ScrollOffset& offset) {
+  Compositor* compositor = GetCompositor();
+  bool scrolled_on_impl_side =
+      compositor && compositor->ScrollLayerTo(cc_layer_->id(), offset);
+
+  if (!scrolled_on_impl_side)
+    cc_layer_->SetScrollOffset(offset);
+
+  DCHECK_EQ(offset.x(), CurrentScrollOffset().x());
+  DCHECK_EQ(offset.y(), CurrentScrollOffset().y());
+}
+
+void Layer::SetScrollable(Layer* parent_clip_layer,
+                          bool can_overscroll,
+                          const base::Closure& on_scroll) {
+  cc_layer_->SetScrollParent(parent_clip_layer->cc_layer_);
+  cc_layer_->SetIsContainerForFixedPositionLayers(true);
+  cc_layer_->SetScrollClipAndCanOverscroll(parent_clip_layer->cc_layer_->id(),
+                                           can_overscroll);
+  cc_layer_->set_did_scroll_callback(on_scroll);
+  cc_layer_->SetUserScrollable(true, true);
+}
+
 void Layer::SetTextureMailbox(
     const cc::TextureMailbox& mailbox,
     std::unique_ptr<cc::SingleReleaseCallback> release_callback,