Changes dip conversions to ceil size and floor origin

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. 
+// 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_