Refactor the PlatformContext layer to have only one class.

base/gfx/native_theme.cc

 // Copyright (c) 2006-2008 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 "base/gfx/native_theme.h"
 
 #include <windows.h>
 #include <uxtheme.h>
 #include <vsstyle.h>
 #include <vssym32.h>
@@ skipping 312 matching lines @@
   return S_OK;
 }
 
 HRESULT NativeTheme::PaintScrollbarTrack(
     HDC hdc,
     int part_id,
     int state_id,
     int classic_state,
     RECT* target_rect,
     RECT* align_rect,
-    skia::PlatformCanvasWin* canvas) const {
+    skia::PlatformCanvas* canvas) const {
   HANDLE handle = GetThemeHandle(SCROLLBAR);
   if (handle && draw_theme_)
     return draw_theme_(handle, hdc, part_id, state_id, target_rect, NULL);
 
   // Draw it manually.
   const DWORD colorScrollbar = GetSysColor(COLOR_SCROLLBAR);
   const DWORD color3DFace = GetSysColor(COLOR_3DFACE);
   if ((colorScrollbar != color3DFace) &&
       (colorScrollbar != GetSysColor(COLOR_WINDOW))) {
     FillRect(hdc, target_rect, reinterpret_cast<HBRUSH>(COLOR_SCROLLBAR + 1));
@@ skipping 50 matching lines @@
   // Classic just renders a flat color background.
   FillRect(hdc, rect, reinterpret_cast<HBRUSH>(COLOR_3DFACE + 1));
   return S_OK;
 }
 
 HRESULT NativeTheme::PaintTrackbar(HDC hdc,
                                    int part_id,
                                    int state_id,
                                    int classic_state,
                                    RECT* rect,
-                                   skia::PlatformCanvasWin* canvas) const {
+                                   skia::PlatformCanvas* canvas) const {
   // Make the channel be 4 px thick in the center of the supplied rect.  (4 px
   // matches what XP does in various menus; GetThemePartSize() doesn't seem to
   // return good values here.)
   RECT channel_rect = *rect;
   const int channel_thickness = 4;
   if (part_id == TKP_TRACK) {
     channel_rect.top +=
         ((channel_rect.bottom - channel_rect.top - channel_thickness) / 2);
     channel_rect.bottom = channel_rect.top + channel_thickness;
   } else if (part_id == TKP_TRACKVERT) {
@@ skipping 286 matching lines @@
     handle = open_theme_(NULL, L"Window");
     break;
   default:
     NOTREACHED();
   }
   theme_handles_[theme_name] = handle;
   return handle;
 }
 
 }  // namespace gfx