Enable hidpi on Linux, refactor a bit on Windows to share

ui/gfx/canvas_paint_win.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 "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/canvas_skia_paint.h"
 #include "ui/gfx/rect.h"
 
@@ skipping 37 matching lines @@
 }
 
 void CanvasSkiaPaint::Init(bool opaque) {
   // 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;
 
-  RecreateBackingCanvas(gfx::Size(width, height),
-      gfx::win::GetDeviceScaleFactor(),
-      opaque);
+  RecreateBackingCanvas(
+      gfx::Size(width, height), gfx::GetDeviceScaleFactor(), 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(
-      -ps_.rcPaint.left / gfx::win::GetDeviceScaleFactor(),
-      -ps_.rcPaint.top / gfx::win::GetDeviceScaleFactor());
+  canvas->translate(-ps_.rcPaint.left / gfx::GetDeviceScaleFactor(),
+                    -ps_.rcPaint.top / gfx::GetDeviceScaleFactor());
 }
 
 }  // namespace gfx