Simplify platform_canvas.h by recognizing that PlatformCanvas does not actually extend

ui/gfx/canvas_paint_win.h

 // Copyright (c) 2011 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_GFX_CANVAS_PAINT_WIN_H_
 #define UI_GFX_CANVAS_PAINT_WIN_H_
 
 #include "skia/ext/platform_canvas.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/canvas_paint.h"
+#include "ui/gfx/size.h"
 
 namespace gfx {
 
 // A class designed to help with WM_PAINT operations on Windows. It will
 // do BeginPaint/EndPaint on init/destruction, and will create the bitmap and
 // canvas with the correct size and transform for the dirty rect. The bitmap
 // will be automatically painted to the screen on destruction.
 //
 // You MUST call isEmpty before painting to determine if anything needs
 // painting. Sometimes the dirty rect can actually be empty, and this makes
@@ skipping 74 matching lines @@
   PAINTSTRUCT ps_;
 
  private:
   void initPaint(bool opaque) {
     paint_dc_ = BeginPaint(hwnd_, &ps_);
 
     init(opaque);
   }
 
   void init(bool opaque) {
-    skia::PlatformCanvas* canvas = platform_canvas();
     // FIXME(brettw) for ClearType, we probably want to expand the bounds of
     // painting by one pixel so that the boundaries will be correct (ClearType
     // text can depend on the adjacent pixel). Then we would paint just the
     // inset pixels to the screen.
     const int width = ps_.rcPaint.right - ps_.rcPaint.left;
     const int height = ps_.rcPaint.bottom - ps_.rcPaint.top;
-    if (!canvas->initialize(width, height, opaque, NULL)) {
-      // Cause a deliberate crash;
-      __debugbreak();
-      _exit(1);
-    }
+
+    RecreateBackingCanvas(gfx::Size(width, height), ui::SCALE_FACTOR_100P,
+                          opaque);
+    skia::PlatformCanvas* canvas = platform_canvas();
+
     canvas->clear(SkColorSetARGB(0, 0, 0, 0));
 
     // This will bring the canvas into the screen coordinate system for the
     // dirty rect
     canvas->translate(SkIntToScalar(-ps_.rcPaint.left),
                       SkIntToScalar(-ps_.rcPaint.top));
   }
 
   // If true, this canvas was created for a BeginPaint.
   const bool for_paint_;
 
   // Disallow copy and assign.
   CanvasSkiaPaint(const CanvasSkiaPaint&);
   CanvasSkiaPaint& operator=(const CanvasSkiaPaint&);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_CANVAS_PAINT_WIN_H_