Render aura scrollbars programmatically instead of with ninebox assets.

ui/native_theme/native_theme_base.h

 // Copyright (c) 2012 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 UI_NATIVE_THEME_NATIVE_THEME_BASE_H_
 #define UI_NATIVE_THEME_NATIVE_THEME_BASE_H_
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 116 matching lines @@
       State state,
       const gfx::Rect& rect,
       const InnerSpinButtonExtraParams& spin_button) const;
 
   virtual void PaintProgressBar(
       SkCanvas* canvas,
       State state,
       const gfx::Rect& rect,
       const ProgressBarExtraParams& progress_bar) const;
 
-  virtual void PaintScrollbarThumbStateTransition(
-      SkCanvas* canvas,
-      State startState,
-      State endState,
-      double progress,
-      const gfx::Rect& rect) const {}
+  virtual void PaintScrollbarThumbStateTransition(SkCanvas* canvas,
+                                                  Part part,
+                                                  State startState,
+                                                  State endState,
+                                                  double progress,
+                                                  const gfx::Rect& rect) const {
+  }
 
   // Shrinks checkbox/radio button rect, if necessary, to make room for padding
   // and drop shadow.
   // TODO(mohsen): This is needed because checkboxes/radio buttons on Android
   // have different padding from those on desktop Chrome. Get rid of this when
   // crbug.com/530746 is resolved.
   virtual void AdjustCheckboxRadioRectForPadding(SkRect* rect) const;
 
   void set_scrollbar_button_length(unsigned int length) {
     scrollbar_button_length_ = length;
@@ skipping 54 matching lines @@
 
   // The length of the arrow buttons, 0 means no buttons are drawn.
   unsigned int scrollbar_button_length_;
 
   DISALLOW_COPY_AND_ASSIGN(NativeThemeBase);
 };
 
 }  // namespace ui
 
 #endif  // UI_NATIVE_THEME_NATIVE_THEME_BASE_H_