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

cc/layers/nine_patch_layer_impl.h

Index: cc/layers/nine_patch_layer_impl.h
diff --git a/cc/layers/nine_patch_layer_impl.h b/cc/layers/nine_patch_layer_impl.h
index c7a1c2e8b28010932cc7be852bdca437a260cd67..69b039a54e7bbfd6fc360d895ad1cbcd5ca4317c 100644
--- a/cc/layers/nine_patch_layer_impl.h
+++ b/cc/layers/nine_patch_layer_impl.h
@@ -12,6 +12,7 @@
 #include "cc/base/cc_export.h"
 #include "cc/layers/layer_impl.h"
 #include "cc/layers/ui_resource_layer_impl.h"
+#include "cc/quads/nine_patch_generator.h"
 #include "cc/resources/resource_provider.h"
 #include "cc/resources/ui_resource_client.h"
 #include "ui/gfx/geometry/rect.h"
@@ -31,52 +32,7 @@ class CC_EXPORT NinePatchLayerImpl : public UIResourceLayerImpl {
   }
   ~NinePatchLayerImpl() override;
 
-  // The bitmap stretches out the bounds of the layer.  The following picture
-  // illustrates the parameters associated with the dimensions.
-  //
-  // Layer space layout
-  //
-  // --------------------------------
-  // |         :    :               |
-  // |         J    C               |
-  // |         :    :               |
-  // |      ------------------      |
-  // |      |       :        |      |
-  // |~~~I~~|  ------------  |      |
-  // |      |  |          |  |      |
-  // |      |  |          |  |      |
-  // |~~~A~~|~~|          |~~|~B~~~~|
-  // |      |  |          |  |      |
-  // |      L  ------------  |      |
-  // |      |       :        |      |
-  // |      ---K--------------      |
-  // |              D               |
-  // |              :               |
-  // |              :               |
-  // --------------------------------
-  //
-  // Bitmap space layout
-  //
-  // ~~~~~~~~~~ W ~~~~~~~~~~
-  // :     :                |
-  // :     Y                |
-  // :     :                |
-  // :~~X~~------------     |
-  // :     |          :     |
-  // :     |          :     |
-  // H     |          Q     |
-  // :     |          :     |
-  // :     ~~~~~P~~~~~      |
-  // :                      |
-  // :                      |
-  // :                      |
-  // ------------------------
-  //
-  // |image_bounds| = (W, H)
-  // |image_aperture| = (X, Y, P, Q)
-  // |border| = (A, C, A + B, C + D)
-  // |occlusion_rectangle| = (I, J, K, L)
-  // |fill_center| indicates whether to draw the center quad or not.
+  // For parameter meanings, see the declaration of NinePatchGenerator.
   void SetLayout(const gfx::Rect& image_aperture,
                  const gfx::Rect& border,
                  const gfx::Rect& layer_occlusion,
@@ -95,33 +51,9 @@ class CC_EXPORT NinePatchLayerImpl : public UIResourceLayerImpl {
   NinePatchLayerImpl(LayerTreeImpl* tree_impl, int id);
 
  private:
-  class Patch {
-   public:
-    Patch(const gfx::RectF& image_rect, const gfx::RectF& layer_rect);
-
-    gfx::RectF image_rect;
-    gfx::RectF layer_rect;
-  };
-
   const char* LayerTypeAsString() const override;
 
-  void CheckGeometryLimitations();
-
-  std::vector<Patch> ComputeQuadsWithOcclusion() const;
-  std::vector<Patch> ComputeQuadsWithoutOcclusion() const;
-
-  // The transparent center region that shows the parent layer's contents in
-  // image space.
-  gfx::Rect image_aperture_;
-
-  // An inset border that the patches will be mapped to.
-  gfx::Rect border_;
-
-  bool fill_center_;
-
-  bool nearest_neighbor_;
-
-  gfx::Rect layer_occlusion_;
+  NinePatchGenerator quad_generator_;
 
   DISALLOW_COPY_AND_ASSIGN(NinePatchLayerImpl);
 };