ui/gfx: split out code that depends on paint

ui/native_theme/native_theme_mac.mm

 // Copyright (c) 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 "ui/native_theme/native_theme_mac.h"
 
 #import <Cocoa/Cocoa.h>
 #include <stddef.h>
 
 #include "base/mac/mac_util.h"
 #include "base/mac/scoped_cftyperef.h"
 #include "base/mac/sdk_forward_declarations.h"
 #include "base/macros.h"
 #import "skia/ext/skia_utils_mac.h"
 #include "third_party/skia/include/core/SkDrawLooper.h"
 #include "third_party/skia/include/core/SkRRect.h"
 #include "third_party/skia/include/effects/SkGradientShader.h"
 #include "ui/base/material_design/material_design_controller.h"
 #include "ui/gfx/color_palette.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/shadow_value.h"
+#include "ui/gfx/skia_paint_util.h"
 #include "ui/gfx/skia_util.h"
 #include "ui/native_theme/common_theme.h"
 
 namespace {
 
 // Values calculated by reading pixels and solving simultaneous equations
 // derived from "A over B" alpha compositing. Steps: Sample the semi-transparent
 // pixel over two backgrounds; P1, P2 over backgrounds B1, B2. Use the color
 // value between 0.0 and 1.0 (i.e. divide by 255.0). Then,
 // alpha = (P2 - P1 + B1 - B2) / (B1 - B2)
@@ skipping 402 matching lines @@
   canvas->drawDRRect(outer_shape, shape, paint);
 }
 
 NativeThemeMac::NativeThemeMac() {
 }
 
 NativeThemeMac::~NativeThemeMac() {
 }
 
 }  // namespace ui