Update the nine patch layer to use UI resources

cc/layers/painted_scrollbar_layer.cc

 // Copyright 2013 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.
 
 #include "cc/layers/painted_scrollbar_layer.h"
 
 #include "base/auto_reset.h"
 #include "base/basictypes.h"
 #include "base/debug/trace_event.h"
 #include "cc/layers/painted_scrollbar_layer_impl.h"
@@ skipping 192 matching lines @@
   gfx::Rect thumb_rect = OriginThumbRect();
 
   if (scrollbar_->HasThumb() && !thumb_rect.IsEmpty()) {
     thumb_resource_ = ScopedUIResource::Create(
         layer_tree_host(), RasterizeScrollbarPart(thumb_rect, THUMB));
   }
 
   return true;
 }
 
-scoped_refptr<UIResourceBitmap> PaintedScrollbarLayer::RasterizeScrollbarPart(
+UIResourceBitmap PaintedScrollbarLayer::RasterizeScrollbarPart(
     gfx::Rect rect,
     ScrollbarPart part) {
   DCHECK(!rect.size().IsEmpty());
 
-  scoped_refptr<UIResourceBitmap> bitmap =
-      UIResourceBitmap::Create(new uint8_t[rect.width() * rect.height() * 4],
-                               UIResourceBitmap::RGBA8,
-                               UIResourceBitmap::CLAMP_TO_EDGE,
-                               rect.size());
-
   SkBitmap skbitmap;
   skbitmap.setConfig(SkBitmap::kARGB_8888_Config, rect.width(), rect.height());
-  skbitmap.setPixels(bitmap->GetPixels());
+  skbitmap.allocPixels();
 
   SkCanvas skcanvas(skbitmap);
   skcanvas.translate(SkFloatToScalar(-rect.x()), SkFloatToScalar(-rect.y()));
   skcanvas.scale(SkFloatToScalar(contents_scale_x()),
                  SkFloatToScalar(contents_scale_y()));
 
   gfx::Rect layer_rect = gfx::ScaleToEnclosingRect(
       rect, 1.f / contents_scale_x(), 1.f / contents_scale_y());
   SkRect layer_skrect = RectToSkRect(layer_rect);
   SkPaint paint;
   paint.setAntiAlias(false);
   paint.setXfermodeMode(SkXfermode::kClear_Mode);
   skcanvas.drawRect(layer_skrect, paint);
   skcanvas.clipRect(layer_skrect);
 
   scrollbar_->PaintPart(&skcanvas, part, layer_rect);
+  // Make sure that the pixels are no longer mutable to unavoid unnecessary
+  // allocation and copying.
+  skbitmap.setImmutable();
 
-  return bitmap;
+  return UIResourceBitmap(skbitmap);
 }
 
 }  // namespace cc