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

ui/gfx/win/dpi.h

-// 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.
-
-#ifndef UI_GFX_DPI_WIN_H_
-#define UI_GFX_DPI_WIN_H_
-
-#include "ui/gfx/gfx_export.h"
-#include "ui/gfx/point.h"
-#include "ui/gfx/rect.h"
-#include "ui/gfx/size.h"
-
-namespace gfx {
-
-// Initialization of the scale factor that should be applied for rendering
-// in this process. Must be called before attempts to call any of the getter
-// methods below in this file, e.g. in the early toolkit/resource bundle setup.
-// This can be called multiple times during various tests, but subsequent calls
-// have no effect.
-GFX_EXPORT void InitDeviceScaleFactor(float scale);
-
-GFX_EXPORT Size GetDPI();
-
-// Gets the scale factor of the display. For example, if the display DPI is
-// 96 then the scale factor is 1.0.
-GFX_EXPORT float GetDPIScale();
-
-// Tests to see if the command line flag "--high-dpi-support" is set.
-GFX_EXPORT bool IsHighDPIEnabled();
-
-GFX_EXPORT bool IsInHighDPIMode();
-
-GFX_EXPORT void EnableHighDPISupport();
-
-GFX_EXPORT void ForceHighDPISupportForTesting(float scale);
-
-// TODO(kevers|girard):  Move above methods into win namespace.
-
-namespace win {
-
-GFX_EXPORT float GetDeviceScaleFactor();
-
-GFX_EXPORT Point ScreenToDIPPoint(const Point& pixel_point);
-
-GFX_EXPORT Point DIPToScreenPoint(const Point& dip_point);
-
-// WARNING: there is no right way to scale sizes and rects. The implementation
-// of these strives to maintain a constant size by scaling the size independent
-// of the origin. An alternative is to get the enclosing rect, which is the
-// right way for some situations. Understand which you need before blindly
-// assuming this is the right way.
-GFX_EXPORT Rect ScreenToDIPRect(const Rect& pixel_bounds);
-GFX_EXPORT Rect DIPToScreenRect(const Rect& dip_bounds);
-GFX_EXPORT Size ScreenToDIPSize(const Size& size_in_pixels);
-GFX_EXPORT Size DIPToScreenSize(const Size& dip_size);
-
-// Win32's GetSystemMetrics uses pixel measures. This function calls
-// GetSystemMetrics for the given |metric|, then converts the result to DIP.
-GFX_EXPORT int GetSystemMetricsInDIP(int metric);
-
-// Returns true if the global device scale factor has been explicitly set for
-// the process.
-GFX_EXPORT bool IsDeviceScaleFactorSet();
-
-GFX_EXPORT extern const wchar_t kRegistryProfilePath[];
-GFX_EXPORT extern const wchar_t kHighDPISupportW[];
-
-}  // namespace win
-}  // namespace gfx
-
-#endif  // UI_GFX_DPI_WIN_H_