Do not convert from RectF to Rect by flooring.

ui/gfx/size_base_impl.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.
 
 #include "ui/gfx/size_base.h"
 
 #include "base/logging.h"
 #include "base/stringprintf.h"
 
 // This file provides the implementation for SizeBaese template and
 // used to instantiate the base class for Size and SizeF classes.
 #if !defined(UI_IMPLEMENTATION)
 #error "This file is intended for UI implementation only"
 #endif
 
 namespace gfx {
 
 template<typename Class, typename Type>
-SizeBase<Class, Type>::SizeBase(Type width, Type height) {
+SizeBase<Class, Type>::SizeBase(Type width, Type height)
+    : allow_negative_size_(false),
+      crash_if_negative_(false) {
   set_width(width);
   set_height(height);
 }
 
 template<typename Class, typename Type>
 SizeBase<Class, Type>::~SizeBase() {}
 
 template<typename Class, typename Type>
 void SizeBase<Class, Type>::set_width(Type width) {
-  if (width < 0) {
-    NOTREACHED() << "negative width:" << width;
+  if (!allow_negative_size_ && width < 0) {
+    if (crash_if_negative_)
+      NOTREACHED() << "negative width:" << width;
     width = 0;
   }
   width_ = width;
 }
 
 template<typename Class, typename Type>
 void SizeBase<Class, Type>::set_height(Type height) {
-  if (height < 0) {
-    NOTREACHED() << "negative height:" << height;
+  if (!allow_negative_size_ && height < 0) {
+    if (crash_if_negative_)
+      NOTREACHED() << "negative height:" << height;
     height = 0;
   }
   height_ = height;
 }
 
 }  // namespace gfx