Scroll with Layers in views::ScrollView

ui/views/controls/scroll_view.h

Index: ui/views/controls/scroll_view.h
diff --git a/ui/views/controls/scroll_view.h b/ui/views/controls/scroll_view.h
index 42348fc536898c984b7b767e9cdbdd5f4b03c0e3..d3ab9bc94633221786e33d8c56bfdc7e91c298b3 100644
--- a/ui/views/controls/scroll_view.h
+++ b/ui/views/controls/scroll_view.h
@@ -12,6 +12,10 @@
 #include "base/macros.h"
 #include "ui/views/controls/scrollbar/scroll_bar.h"
 
+namespace gfx {
+class ScrollOffset;
+}
+
 namespace views {
 namespace test {
 class ScrollViewTestApi;
@@ -89,6 +93,7 @@ class VIEWS_EXPORT ScrollView : public View, public ScrollBarController {
   void OnMouseExited(const ui::MouseEvent& event) override;
   void OnGestureEvent(ui::GestureEvent* event) override;
   const char* GetClassName() const override;
+  ScrollView* EnclosingScrollView() override;
 
   // ScrollBarController overrides:
   void ScrollToPosition(ScrollBar* source, int position) override;
@@ -125,9 +130,24 @@ class VIEWS_EXPORT ScrollView : public View, public ScrollBarController {
   // Update the scrollbars positions given viewport and content sizes.
   void UpdateScrollBarPositions();
 
-  // The current contents and its viewport. |contents_| is contained in
-  // |contents_viewport_|.
+  // Helpers to get and set the current scroll offset (either from the ui::Layer
+  // or from the |contents_| origin offset).
+  gfx::ScrollOffset CurrentOffset() const;
+  void ScrollToOffset(const gfx::ScrollOffset& offset);
+
+  // Callback entrypoint when hosted Layers are scrolled by the Compositor.
+  void OnLayerScrolled();
+
+  // Horizontally scrolls the header (if any) to match the contents.
+  void ScrollHeader();
+
+  // The current contents and its viewport. |contents_| is contained in the
+  // layer-backed |contents_container_| which guarantees it is at least as high
+  // and wide as the |contents_viewport_|, which does the clipping. If
+  // |contents_container_| is null, the origin of |contents_| is offset to
+  // perform scrolling.
   View* contents_;
+  View* contents_container_;
   View* contents_viewport_;
 
   // The current header and its viewport. |header_| is contained in