Add additional error handling and null checking to ImageSkiaOperations

ui/gfx/image/image_skia_rep.cc

 // 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/image/image_skia_rep.h"
 
-#include "ui/gfx/size.h"
-
 namespace gfx {
 
 ImageSkiaRep::ImageSkiaRep()
     : scale_factor_(ui::SCALE_FACTOR_NONE) {
 }
 
 ImageSkiaRep::~ImageSkiaRep() {
 }
 
 ImageSkiaRep::ImageSkiaRep(const gfx::Size& size,
@@ skipping 20 matching lines @@
 int ImageSkiaRep::GetHeight() const {
   return static_cast<int>(bitmap_.height() /
       ui::GetScaleFactorScale(scale_factor_));
 }
 
 float ImageSkiaRep::GetScale() const {
   return ui::GetScaleFactorScale(scale_factor_);
 }
 
 }  // namespace gfx