Use C++11 features in core/html

Source/core/html/canvas/WebGLTexture.cpp

Index: Source/core/html/canvas/WebGLTexture.cpp
diff --git a/Source/core/html/canvas/WebGLTexture.cpp b/Source/core/html/canvas/WebGLTexture.cpp
index 8cce398370578d9ce519438e2527c3640a429e4e..c6e347f0adba5db5ca62d58a52d2fe1ff48e436c 100644
--- a/Source/core/html/canvas/WebGLTexture.cpp
+++ b/Source/core/html/canvas/WebGLTexture.cpp
@@ -378,12 +378,12 @@ void WebGLTexture::update()
 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]);
 }