Use C++11 features in core/html

Source/core/html/canvas/WebGLTexture.cpp

 /*
  * Copyright (C) 2009 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 360 matching lines @@
     if (m_info.size() > 1 && !m_isCubeComplete)
         m_needToUseBlackTexture = true;
     // Completeness
     if (!m_isComplete && m_minFilter != GL_NEAREST && m_minFilter != GL_LINEAR)
         m_needToUseBlackTexture = true;
 }
 
 const WebGLTexture::LevelInfo* WebGLTexture::getLevelInfo(GLenum target, GLint level) const
 {
     if (!object() || !m_target)
-        return 0;
+        return nullptr;
     int targetIndex = mapTargetToIndex(target);
     if (targetIndex < 0 || targetIndex >= static_cast<int>(m_info.size()))
-        return 0;
+        return nullptr;
     if (level < 0 || level >= static_cast<GLint>(m_info[targetIndex].size()))
-        return 0;
+        return nullptr;
     return &(m_info[targetIndex][level]);
 }
 
 }