Implement pinch-zoom scaling for main-frame scrollbars and pinch-zoom overlay scrollbars.

cc/pinch_zoom_viewport.h

Index: cc/pinch_zoom_viewport.h
diff --git a/cc/pinch_zoom_viewport.h b/cc/pinch_zoom_viewport.h
index 0b55a3fe97df425ff9806172abb22739a1e92221..7c70a261cef219c168916b5beab975cd557e3c05 100644
--- a/cc/pinch_zoom_viewport.h
+++ b/cc/pinch_zoom_viewport.h
@@ -6,18 +6,22 @@
 #define CC_PINCH_ZOOM_VIEWPORT_H_
 
 #include "cc/cc_export.h"
+#include "cc/pinch_zoom_scrollbar_layer_impl.h"
 #include "ui/gfx/rect.h"
 #include "ui/gfx/transform.h"
 
 namespace cc {
 
+class LayerTreeHostImpl;
+
 // PinchZoomViewport models the bounds and offset of the viewport that is used
 // during a pinch-zoom operation. It tracks the layout-space dimensions of the
 // viewport before any applied scale, and then tracks the layout-space
 // coordinates of the viewport respecting the pinch settings.
 class CC_EXPORT PinchZoomViewport {
  public:
-  PinchZoomViewport();
+  PinchZoomViewport(LayerTreeHostImpl*);
+  ~PinchZoomViewport();
 
   float total_page_scale_factor() const {
     return page_scale_factor_ * page_scale_delta_;
@@ -58,6 +62,9 @@ class CC_EXPORT PinchZoomViewport {
   void set_layout_viewport_size(const gfx::SizeF& size) {
     layout_viewport_size_ = size;
   }
+  gfx::SizeF layout_viewport_size() {
+    return layout_viewport_size_;
+  }
 
   // Apply the scroll offset in layout space to the offset of the pinch-zoom
   // viewport. The viewport cannot be scrolled outside of the layout viewport
@@ -71,6 +78,11 @@ class CC_EXPORT PinchZoomViewport {
   // implTransform = S[pageScale] * Tr[-zoomedDeviceViewportOffset]
   gfx::Transform ImplTransform(bool page_scale_pinch_zoom_enabled) const;
 
+  LayerImpl* root_scroll_layer();
+  LayerImpl* currently_scrolling_layer() const;
+
+  void AddPinchZoomScrollbarsToTree(LayerTreeImpl*);
+
  private:
   float page_scale_factor_;
   float page_scale_delta_;
@@ -81,6 +93,10 @@ class CC_EXPORT PinchZoomViewport {
 
   gfx::Vector2dF zoomed_viewport_offset_;
   gfx::SizeF layout_viewport_size_;
+
+  PinchZoomScrollbarState vertical_scrollbar_client_;
+  PinchZoomScrollbarState horizontal_scrollbar_client_;
+  LayerTreeHostImpl* owner_;
 };
 
 }  // namespace cc