cc: Set up the framework to restrict access to Layer internals.

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 <algorithm>
 
 #include "base/auto_reset.h"
 #include "cc/base/math_util.h"
@@ skipping 227 matching lines @@
     }
     return updated;
   }
 
   if (!has_thumb_ && thumb_resource_) {
     thumb_resource_ = nullptr;
     SetNeedsPushProperties();
     updated = true;
   }
 
-  if (update_rect_.IsEmpty() && track_resource_)
+  if (update_rect().IsEmpty() && track_resource_)
     return updated;
 
   if (!track_resource_ || scrollbar_->NeedsPaintPart(TRACK)) {
     track_resource_ = ScopedUIResource::Create(
         layer_tree_host(),
         RasterizeScrollbarPart(track_layer_rect, scaled_track_rect, TRACK));
   }
 
   gfx::Rect thumb_layer_rect = OriginThumbRect();
   gfx::Rect scaled_thumb_rect =
@@ skipping 45 matching lines @@
 
   scrollbar_->PaintPart(&skcanvas, part, layer_rect);
   // Make sure that the pixels are no longer mutable to unavoid unnecessary
   // allocation and copying.
   skbitmap.setImmutable();
 
   return UIResourceBitmap(skbitmap);
 }
 
 }  // namespace cc