Refactor the PlatformContext layer to have only one class.

app/gfx/canvas_win.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 "app/gfx/canvas.h"
 
 #include <limits>
 
 #include "app/gfx/font.h"
 #include "app/l10n_util.h"
@@ skipping 102 matching lines @@
     }
   }
   return f;
 }
 
 }  // anonymous namespace
 
 namespace gfx {
 
 Canvas::Canvas(int width, int height, bool is_opaque)
-    : skia::PlatformCanvasWin(width, height, is_opaque) {
+    : skia::PlatformCanvas(width, height, is_opaque) {
 }
 
-Canvas::Canvas() : skia::PlatformCanvasWin() {
+Canvas::Canvas() : skia::PlatformCanvas() {
 }
 
 Canvas::~Canvas() {
 }
 
 // static
 void Canvas::SizeStringInt(const std::wstring& text,
                            const gfx::Font& font,
                            int *width, int *height, int flags) {
   HDC dc = GetDC(NULL);
@@ skipping 122 matching lines @@
         text_row[cur_x] |= 0xff << SK_A32_SHIFT;  // Make opaque.
       }
     }
   }
 
   // Draw the halo bitmap with blur.
   drawBitmap(text_bitmap, SkIntToScalar(x - 1), SkIntToScalar(y - 1));
 }
 
 }  // namespace gfx