Use nine-patch resource for drawing Aura overlay scrollbar thumb.

cc/layers/overlay_scrollbar_layer_impl.h

+// Copyright 2016 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.
+
+#ifndef CC_LAYERS_OVERLAY_SCROLLBAR_LAYER_IMPL_H_
+#define CC_LAYERS_OVERLAY_SCROLLBAR_LAYER_IMPL_H_
+
+#include "base/macros.h"
+#include "cc/base/cc_export.h"
+#include "cc/input/scrollbar.h"
+#include "cc/layers/scrollbar_layer_impl_base.h"
+#include "cc/quads/nine_patch_generator.h"
+#include "cc/resources/ui_resource_client.h"
+
+namespace cc {
+
+class LayerTreeImpl;
+
+class CC_EXPORT OverlayScrollbarLayerImpl : public ScrollbarLayerImplBase {
+ public:
+  static std::unique_ptr<OverlayScrollbarLayerImpl> Create(
+      LayerTreeImpl* tree_impl,
+      int id,
+      ScrollbarOrientation orientation,
+      bool is_left_side_vertical_scrollbar);
+  ~OverlayScrollbarLayerImpl() override;
+
+  // LayerImpl implementation.
+  std::unique_ptr<LayerImpl> CreateLayerImpl(LayerTreeImpl* tree_impl) override;
+  void PushPropertiesTo(LayerImpl* layer) override;
+
+  bool WillDraw(DrawMode draw_mode,
+                ResourceProvider* resource_provider) override;
+  void AppendQuads(RenderPass* render_pass,
+                   AppendQuadsData* append_quads_data) override;
+
+  void SetThumbThickness(int thumb_thickness);
+  void SetThumbLength(int thumb_length);
+  void SetTrackStart(int track_start);
+  void SetTrackLength(int track_length);
+
+  void SetImageBounds(const gfx::Size& bounds);
+  void SetAperture(const gfx::Rect& aperture);
+
+  void set_thumb_ui_resource_id(UIResourceId uid) {
+    thumb_ui_resource_id_ = uid;
+  }
+
+ protected:
+  OverlayScrollbarLayerImpl(LayerTreeImpl* tree_impl,
+                            int id,
+                            ScrollbarOrientation orientation,
+                            bool is_left_side_vertical_scrollbar);
+
+  // ScrollbarLayerImplBase implementation.
+  int ThumbThickness() const override;
+  int ThumbLength() const override;
+  float TrackLength() const override;
+  int TrackStart() const override;
+  bool IsThumbResizable() const override;
+
+ private:
+  const char* LayerTypeAsString() const override;
+
+  UIResourceId thumb_ui_resource_id_;
+
+  int thumb_thickness_;
+  int thumb_length_;
+  int track_start_;
+  int track_length_;
+
+  gfx::Size image_bounds_;
+  gfx::Rect aperture_;
+
+  NinePatchGenerator quad_generator_;
+
+  DISALLOW_COPY_AND_ASSIGN(OverlayScrollbarLayerImpl);
+};
+
+}  // namespace cc
+#endif  // CC_LAYERS_OVERLAY_SCROLLBAR_LAYER_IMPL_H_