Change Aura overlay scrollbars from solid color to painted scrollbars.

ui/native_theme/native_theme_base.cc

 // 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.
 
 #include "ui/native_theme/native_theme_base.h"
 
 #include <limits>
 #include <memory>
 
 #include "base/command_line.h"
@@ skipping 33 matching lines @@
     SkColorSetRGB(0x9d, 0x96, 0x8e);
 
 const SkColor kTextBorderColor = SkColorSetRGB(0xa9, 0xa9, 0xa9);
 
 const SkColor kProgressBorderColor = kTextBorderColor;
 const SkColor kProgressTickColor = SkColorSetRGB(0xED, 0xED, 0xED);
 const SkColor kProgressValueColor = gfx::kGoogleBlue300;
 
 const SkColor kMenuPopupBackgroundColor = SkColorSetRGB(210, 225, 246);
 
-const unsigned int kDefaultScrollbarWidth = 15;
-const unsigned int kDefaultScrollbarButtonLength = 14;
+const int kDefaultScrollbarWidth = 15;
+const int kDefaultScrollbarButtonLength = 14;
 
 const SkColor kCheckboxTinyColor = SK_ColorGRAY;
 const SkColor kCheckboxShadowColor = SkColorSetARGB(0x15, 0, 0, 0);
 const SkColor kCheckboxShadowHoveredColor = SkColorSetARGB(0x1F, 0, 0, 0);
 const SkColor kCheckboxShadowDisabledColor = SkColorSetARGB(0, 0, 0, 0);
 const SkColor kCheckboxGradientColors[] = {
     SkColorSetRGB(0xed, 0xed, 0xed),
     SkColorSetRGB(0xde, 0xde, 0xde) };
 const SkColor kCheckboxGradientPressedColors[] = {
     SkColorSetRGB(0xe7, 0xe7, 0xe7),
@@ skipping 949 matching lines @@
   SkScalar min_diff = Clamp((hsv1[1] + hsv2[1]) * 1.2f, 0.28f, 0.5f);
   SkScalar diff = Clamp(fabs(hsv1[2] - hsv2[2]) / 2, min_diff, 0.5f);
 
   if (hsv1[2] + hsv2[2] > 1.0)
     diff = -diff;
 
   return SaturateAndBrighten(hsv2, -0.2f, diff);
 }
 
 }  // namespace ui