Do not convert from RectF to Rect by flooring.

ui/gfx/rect_conversions.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_RECT_CONVERSIONS_H_
+#define UI_GFX_RECT_CONVERSIONS_H_
+
+#include "ui/gfx/rect.h"
+#include "ui/gfx/rect_f.h"
+
+namespace gfx {
+
+// Returns the smallest Rect that encloses the given RectF.
+UI_EXPORT Rect ToEnclosingRect(const RectF& rect);
+
+// Returns the largest Rect that is enclosed by the given Rect.
+UI_EXPORT Rect ToEnclosedRect(const RectF& rect);
+
+}  // namespace gfx
+
+#endif  // UI_GFX_RECT_CONVERSIONS_H_