Do not convert from RectF to Rect by flooring.

ui/gfx/rect.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.
 
 // Defines a simple integer rectangle class.  The containment semantics
 // are array-like; that is, the coordinate (x, y) is considered to be
 // contained by the rectangle, but the coordinate (x + width, y) is not.
 // The class will happily let you create malformed rectangles (that is,
 // rectangles with negative width and/or height), but there will be assertions
 // in the operations (such as Contains()) to complain in this case.
 
 #ifndef UI_GFX_RECT_H_
 #define UI_GFX_RECT_H_
 
 #include <string>
 
 #include "ui/gfx/point.h"
 #include "ui/gfx/rect_base.h"
+#include "ui/gfx/rect_f.h"
 #include "ui/gfx/size.h"
 
 #if defined(OS_WIN)
 typedef struct tagRECT RECT;
 #elif defined(TOOLKIT_GTK)
 typedef struct _GdkRectangle GdkRectangle;
 #elif defined(OS_IOS)
 #include <CoreGraphics/CoreGraphics.h>
 #elif defined(OS_MACOSX)
 #include <ApplicationServices/ApplicationServices.h>
@@ skipping 31 matching lines @@
 #if defined(OS_WIN)
   // Construct an equivalent Win32 RECT object.
   RECT ToRECT() const;
 #elif defined(TOOLKIT_GTK)
   GdkRectangle ToGdkRectangle() const;
 #elif defined(OS_MACOSX)
   // Construct an equivalent CoreGraphics object.
   CGRect ToCGRect() const;
 #endif
 
+  RectF ToRectF() const WARN_UNUSED_RESULT {
+    return RectF(origin().x(), origin().y(), size().width(), size().height());
+  }
+
+  // This fuction is retained to maintain the old behavior, but should never be
+  // used. Every instance of ScaleUnsafe should be replaced with a Scale
+  // followed by ToEnclosingRect or ToEnclosedRect as appropriate.
+  Rect ScaleUnsafe(float scale) const WARN_UNUSED_RESULT;

[sky, 2012/09/27 17:48:30]

Why do we need these? Can't we pick one and make Scale use it? This is
especially confusing when you've updated BackingStoreAura to use the Unsafe one.

+  Rect ScaleUnsafe(float x_scale, float y_scale) const WARN_UNUSED_RESULT;
+
+  RectF Scale(float scale) const WARN_UNUSED_RESULT {
+    return Scale(scale, scale);
+  }
+
+  RectF Scale(float x_scale, float y_scale) const WARN_UNUSED_RESULT {
+    return ToRectF().Scale(x_scale, y_scale);
+  }
+
   std::string ToString() const;
 };
 
 #if !defined(COMPILER_MSVC)
 extern template class RectBase<Rect, Point, Size, Insets, int>;
 #endif
 
 }  // namespace gfx
 
 #endif  // UI_GFX_RECT_H_